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All trademarks and registered trademarks are the property of their respective owners Contents About ................................................................................................................................................................................... 1 Chapter 1: Getting started with Objective-C Language ............................................................................ 2 Section 1.1: Hello World ................................................................................................................................................. 2 Chapter 2: Basic Data Types .................................................................................................................................. 4 Section 2.1: SEL ............................................................................................................................................................... 4 Section 2.2: BOOL .......................................................................................................................................................... 4 Section 2.3: id ................................................................................................................................................................. 5 Section 2.4: IMP (implementation pointer) ................................................................................................................. 5 Section 2.5: NSInteger and NSUInteger ...................................................................................................................... 6 Chapter 3: Enums .......................................................................................................................................................... 8 Section 3.1: typedef enum declaration in Objective-C ............................................................................................... 8 Section 3.2: Converting C++ std::vector to an Objective-C Array ............................................................... 8 Section 3.3: Defining an enum ...................................................................................................................................... 9 Chapter 4: Structs ...................................................................................................................................................... 10 Section 4.1: Defining a Structure and Accessing Structure Members .................................................................... 10 Section 4.2: CGPoint .................................................................................................................................................... 10 Chapter 5: Classes and Objects .......................................................................................................................... 12 Section 5.1: Dierence between allocation and initialization .................................................................................. 12 Section 5.2: Creating classes with initialization values ............................................................................................ 12 Section 5.3: Specifying Generics ................................................................................................................................ 13 Section 5.4: Singleton Class ........................................................................................................................................ 13 Section 5.5: The "instancetype" return type ............................................................................................................. 14 Chapter 6: Inheritance ............................................................................................................................................. 15 Section 6.1: Car is inherited from Vehicle .................................................................................................................. 15 Chapter 7: Methods ................................................................................................................................................... 17 Section 7.1: Class methods .......................................................................................................................................... 17 Section 7.2: Pass by value parameter passing ........................................................................................................ 17 Section 7.3: Pass by reference parameter passing ................................................................................................. 17 Section 7.4: Method parameters ................................................................................................................................ 18 Section 7.5: Create a basic method ........................................................................................................................... 18 Section 7.6: Return values .......................................................................................................................................... 19 Section 7.7: Calling methods ...................................................................................................................................... 19 Section 7.8: Instance methods ................................................................................................................................... 20 Chapter 8: Properties ............................................................................................................................................... 21 Section 8.1: Custom getters and setters .................................................................................................................... 21 Section 8.2: Properties that cause updates .............................................................................................................. 22 Section 8.3: What are properties? ............................................................................................................................. 23 Chapter 9: Random Integer .................................................................................................................................. 26 Section 9.1: Basic Random Integer ............................................................................................................................ 26 Section 9.2: Random Integer within a Range ........................................................................................................... 26 Chapter 10: BOOL / bool / Boolean / NSCFBoolean ................................................................................ 27 Section 10.1: BOOL/Boolean/bool/NSCFBoolean .................................................................................................... 27 Section 10.2: BOOL VS Boolean ................................................................................................................................. 27 Chapter 11: Continue and Break! ......................................................................................................................... 28 Section 11.1: Continue and Break Statement ............................................................................................................. 28 Chapter 12: Key Value Coding / Key Value Observing ............................................................................ 29 Section 12.1: Most Common Real Life Key Value Coding Example ........................................................................ 29 Section 12.2: Querying KVC Data .............................................................................................................................. 29 Section 12.3: Collection Operators ............................................................................................................................. 30 Section 12.4: Key Value Observing ............................................................................................................................ 32 Chapter 13: NSString ................................................................................................................................................. 35 Section 13.1: Encoding and Decoding ........................................................................................................................ 35 Section 13.2: String Length .......................................................................................................................................... 35 Section 13.3: Comparing Strings ................................................................................................................................. 35 Section 13.4: Splitting ................................................................................................................................................... 36 Section 13.5: Searching for a Substring ..................................................................................................................... 37 Section 13.6: Creation .................................................................................................................................................. 37 Section 13.7: Changing Case ....................................................................................................................................... 38 Section 13.8: Removing Leading and Trailing Whitespace ..................................................................................... 38 Section 13.9: Joining an Array of Strings .................................................................................................................. 38 Section 13.10: Formatting ............................................................................................................................................ 39 Section 13.11: Working with C Strings ......................................................................................................................... 39 Section 13.12: Reversing a NSString Objective-C ...................................................................................................... 39 Chapter 14: NSArray ................................................................................................................................................. 41 Section 14.1: Creating Arrays ...................................................................................................................................... 41 Section 14.2: Accessing elements ............................................................................................................................... 41 Section 14.3: Using Generics ....................................................................................................................................... 41 Section 14.4: Reverse an Array .................................................................................................................................. 42 Section 14.5: Converting between Sets and Arrays ................................................................................................. 42 Section 14.6: Converting NSArray to NSMutableArray to allow modification ....................................................... 42 Section 14.7: Looping through .................................................................................................................................... 42 Section 14.8: Enumerating using blocks .................................................................................................................... 43 Section 14.9: Comparing arrays ................................................................................................................................. 43 Section 14.10: Filtering Arrays With Predicates ......................................................................................................... 43 Section 14.11: Sorting array with custom objects ...................................................................................................... 44 Section 14.12: Sorting Arrays ...................................................................................................................................... 44 Section 14.13: Filter NSArray and NSMutableArray .................................................................................................. 45 Section 14.14: Add objects to NSArray ....................................................................................................................... 45 Section 14.15: Finding out the Number of Elements in an Array ............................................................................. 45 Section 14.16: Creating NSArray instances ................................................................................................................ 45 Chapter 15: NSMutableArray ................................................................................................................................ 46 Section 15.1: Sorting Arrays ......................................................................................................................................... 46 Section 15.2: Creating an NSMutableArray ............................................................................................................... 46 Section 15.3: Adding elements .................................................................................................................................... 46 Section 15.4: Insert Elements ...................................................................................................................................... 46 Section 15.5: Deleting Elements .................................................................................................................................. 46 Section 15.6: Move object to another index .............................................................................................................. 47 Section 15.7: Filtering Array content with Predicate ................................................................................................ 47 Chapter 16: NSDictionary ........................................................................................................................................ 48 Section 16.1: Create ...................................................................................................................................................... 48 Section 16.2: Fast Enumeration .................................................................................................................................. 48 Section 16.3: Creating using literals ........................................................................................................................... 48 Section 16.4: Creating using dictionaryWithObjectsAndKeys: ................................................................................ 48 Section 16.5: NSDictionary to NSArray ...................................................................................................................... 49 Section 16.6: NSDictionary to NSData ....................................................................................................................... 49 Section 16.7: NSDictionary to JSON ........................................................................................................................... 49 Section 16.8: Creating using plists .............................................................................................................................. 49 Section 16.9: Setting a Value in NSDictionary ........................................................................................................... 49 Section 16.10: Getting a Value from NSDictionary ................................................................................................... 50 Section 16.11: Check if NSDictionary already has a key or not ............................................................................... 50 Section 16.12: Block Based Enumeration ................................................................................................................... 50 Chapter 17: NSMutableDictionary ...................................................................................................................... 52 Section 17.1: NSMutableDictionary Example ............................................................................................................. 52 Section 17.2: Removing Entries From a Mutable Dictionary ................................................................................... 53 Chapter 18: NSDate .................................................................................................................................................... 55 Section 18.1: Convert NSDate that is composed from hour and minute (only) to a full NSDate ........................ 55 Section 18.2: Converting NSDate to NSString ........................................................................................................... 55 Section 18.3: Creating an NSDate .............................................................................................................................. 56 Section 18.4: Date Comparison .................................................................................................................................. 56 Chapter 19: NSURL ..................................................................................................................................................... 58 Section 19.1: Create ...................................................................................................................................................... 58 Section 19.2: Compare NSURL ................................................................................................................................... 58 Section 19.3: Modifying and Converting a File URL with removing and appending path .................................... 58 Chapter 20: NSUrl send a post request .......................................................................................................... 60 Section 20.1: Simple POST request ............................................................................................................................ 60 Section 20.2: Simple Post Request With Timeout .................................................................................................... 60 Chapter 21: NSData .................................................................................................................................................... 61 Section 21.1: Create ...................................................................................................................................................... 61 Section 21.2: NSData and Hexadecimal String ......................................................................................................... 61 Section 21.3: Get NSData length ................................................................................................................................ 62 Section 21.4: Encoding and decoding a string using NSData Base64 ................................................................... 62 Chapter 22: NSPredicate ......................................................................................................................................... 63 Section 22.1: Filter By Name ....................................................................................................................................... 63 Section 22.2: Find movies except given ids .............................................................................................................. 64 Section 22.3: Find all the objects which is of type movie ........................................................................................ 64 Section 22.4: Find Distinct object ids of array .......................................................................................................... 64 Section 22.5: Find movies with specific ids ............................................................................................................... 64 Section 22.6: Case Insensitive comparison with exact title match ......................................................................... 64 Section 22.7: Case sensitive with exact title match .................................................................................................. 64 Section 22.8: Case Insensitive comparison with matching subset ......................................................................... 65 Chapter 23: NSRegularExpression ..................................................................................................................... 66 Section 23.1: Check whether a string matches a pattern ........................................................................................ 66 Section 23.2: Find all the numbers in a string .......................................................................................................... 66 Chapter 24: NSJSONSerialization ...................................................................................................................... 67 Section 24.1: JSON Parsing using NSJSONSerialization Objective-C ..................................................................... 67 Chapter 25: NSCalendar .......................................................................................................................................... 69 Section 25.1: System Locale Information .................................................................................................................. 69 Section 25.2: Initializing a Calendar ........................................................................................................................... 69 Section 25.3: Calendrical Calculations ...................................................................................................................... 69 Chapter 26: NSAttributedString .......................................................................................................................... 71 Section 26.1: Using Enumerating over Attributes in a String and underline part of string .................................. 71 Section 26.2: Creating a string that has custom kerning (letter spacing) editshare ........................................... 71 Section 26.3: Create a string with text struck through ............................................................................................ 71 Section 26.4: How you create a tri-color attributed string ..................................................................................... 72 Chapter 27: NSTimer ................................................................................................................................................. 73 Section 27.1: Storing information in the Timer .......................................................................................................... 73 Section 27.2: Creating a Timer ................................................................................................................................... 73 Section 27.3: Invalidating a timer ............................................................................................................................... 73 Section 27.4: Manually firing a timer ......................................................................................................................... 74 Chapter 28: NSObject ............................................................................................................................................... 75 Section 28.1: NSObject ................................................................................................................................................ 75 Chapter 29: NSSortDescriptor ............................................................................................................................. 76 Section 29.1: Sorted by combinations of NSSortDescriptor .................................................................................... 76 Chapter 30: NSTextAttachment .......................................................................................................................... 77 Section 30.1: NSTextAttachment Example ................................................................................................................ 77 Chapter 31: NSCache ................................................................................................................................................. 78 Section 31.1: NSCache .................................................................................................................................................. 78 Chapter 32: NSUserDefaults ................................................................................................................................. 79 Section 32.1: Simple example ..................................................................................................................................... 79 Section 32.2: Clear NSUserDefaults .......................................................................................................................... 79 Chapter 33: Subscripting ......................................................................................................................................... 80 Section 33.1: Subscripts with NSArray ....................................................................................................................... 80 Section 33.2: Custom Subscripting ............................................................................................................................ 80 Section 33.3: Subscripts with NSDictionary ............................................................................................................... 80 Chapter 34: Low-level Runtime Environment .............................................................................................. 82 Section 34.1: Augmenting methods using Method Swizzling .................................................................................. 82 Section 34.2: Attach object to another existing object (association) .................................................................... 83 Section 34.3: Calling methods directly ...................................................................................................................... 83 Chapter 35: Fast Enumeration ............................................................................................................................. 85 Section 35.1: Fast enumeration of an NSArray with index ...................................................................................... 85 Section 35.2: Fast enumeration of an NSArray ........................................................................................................ 85 Chapter 36: Categories ............................................................................................................................................ 86 Section 36.1: Conforming to protocol ........................................................................................................................ 86 Section 36.2: Simple Category ................................................................................................................................... 86 Section 36.3: Declaring a class method .................................................................................................................... 86 Section 36.4: Adding a property with a category .................................................................................................... 87 Section 36.5: Create a Category on XCode .............................................................................................................. 87 Chapter 37: Protocols ............................................................................................................................................... 91 Section 37.1: Optional and required methods ........................................................................................................... 91 Section 37.2: Checking existence of optional method implementations ............................................................... 91 Section 37.3: Forward Declarations ........................................................................................................................... 91 Section 37.4: Conforming to Protocols ...................................................................................................................... 92 Section 37.5: Basic Protocol Definition ...................................................................................................................... 92 Section 37.6: Check conforms Protocol .................................................................................................................... 92 Chapter 38: Protocols and Delegates .............................................................................................................. 93 Section 38.1: Implementation of Protocols and Delegation mechanism ............................................................... 93 Chapter 39: Blocks ...................................................................................................................................................... 94 Section 39.1: Block Typedefs ...................................................................................................................................... 94 Section 39.2: Blocks as Properties ............................................................................................................................. 94 Section 39.3: Blocks as local variables ...................................................................................................................... 95 Section 39.4: Blocks as Method Parameters ............................................................................................................ 95 Section 39.5: Defining and Assigning ........................................................................................................................ 95 Chapter 40: XML parsing ........................................................................................................................................ 96 Section 40.1: XML Parsing ........................................................................................................................................... 96 Chapter 41: Declare class method and instance method ...................................................................... 98 Section 41.1: How to declare class method and instance method ......................................................................... 98 Chapter 42: Predefined Macros .......................................................................................................................... 99 Section 42.1: Predefined Macros ................................................................................................................................ 99 Chapter 43: Grand Central Dispatch .............................................................................................................. 100 Section 43.1: What is Grand central dispatch ......................................................................................................... 100 Chapter 44: Format-Specifiers ......................................................................................................................... 101 Section 44.1: Integer Example - %i ........................................................................................................................... 101 Chapter 45: Logging ............................................................................................................................................... 102 Section 45.1: Logging ................................................................................................................................................ 102 Section 45.2: NSLog Output Format ....................................................................................................................... 102 Section 45.3: Removing Log Statements from Release Builds ............................................................................ 102 Section 45.4: Logging Variable Values ................................................................................................................... 102 Section 45.5: Empty message is not printed .......................................................................................................... 103 Section 45.6: Using __FUNCTION __ ..................................................................................................................... 103 Section 45.7: NSLog vs printf ................................................................................................................................... 103 Section 45.8: Logging NSLog meta data ................................................................................................................ 104 Section 45.9: NSLog and BOOL type ....................................................................................................................... 104 Section 45.10: Logging by Appending to a File ...................................................................................................... 105 Chapter 46: Error Handling ................................................................................................................................. 106 Section 46.1: Error & Exception handling with try catch block .............................................................................. 106 Section 46.2: Asserting .............................................................................................................................................. 106 Chapter 47: Modern Objective-C ...................................................................................................................... 108 Section 47.1: Literals .................................................................................................................................................. 108 Section 47.2: Container subscripting ....................................................................................................................... 108 Chapter 48: Singletons .......................................................................................................................................... 110 Section 48.1: Using Grand Central Dispatch (GCD) ................................................................................................ 110 Section 48.2: Creating Singleton and also preventing it from having multiple instance using alloc/init, new ............................................................................................................................................................................. 110 Section 48.3: Creating Singleton class and also preventing it from having multiple instances using alloc/init ............................................................................................................................................................. 111 Chapter 49: Multi-Threading .............................................................................................................................. 112 Section 49.1: Creating a simple thread .................................................................................................................... 112 Section 49.2: Create more complex thread ............................................................................................................ 112 Section 49.3: Thread-local storage ......................................................................................................................... 113 Chapter 50: Unit testing using Xcode ............................................................................................................ 114 Section 50.1: Note: ..................................................................................................................................................... 114 Section 50.2: Testing a block of code or some method: ....................................................................................... 114 Section 50.3: Testing asynchronous block of code: .............................................................................................. 114 Section 50.4: Measuring Performance of a block of code: ................................................................................... 115 Section 50.5: Running Test Suits: ............................................................................................................................. 115 Chapter 51: Memory Management .................................................................................................................. 116 Section 51.1: Memory management rules when using manual reference counting ........................................... 116 Section 51.2: Automatic Reference Counting ......................................................................................................... 117 Section 51.3: Strong and weak references .............................................................................................................. 118 Section 51.4: Manual Memory Management .......................................................................................................... 118 Credits ............................................................................................................................................................................ 120 You may also like ...................................................................................................................................................... 122 About Please feel free to share this PDF with anyone for free, latest version of this book can be downloaded from: https://goalkicker.com/ObjectiveCBook This Objective-C® Notes for Professionals book is compiled from Stack Overflow Documentation, the content is written by the beautiful people at Stack Overflow. Text content is released under Creative Commons BY-SA, see credits at the end of this book whom contributed to the various chapters. Images may be copyright of their respective owners unless otherwise specified This is an unofficial free book created for educational purposes and is not affiliated with official Objective-C® group(s) or company(s) nor Stack Overflow. All trademarks and registered trademarks are the property of their respective company owners The information presented in this book is not guaranteed to be correct nor accurate, use at your own risk Please send feedback and corrections to [email protected] GoalKicker.com – Objective-C® Notes for Professionals 1 Chapter 1: Getting started with Objective-C Language Version Release Date 1.0 1983-01-01 2.0 2007-10-27 Modern 2014-03-10 Section 1.1: Hello World This program will output "Hello World!" #import int main(int argc, char * argv[]) { NSLog(@"Hello World!"); } #import is a pre-processor directive, which indicates we want to import or include the information from that file into the program. In this case, the compiler will copy the contents of Foundation.h in the Foundation framework to the top of the file. The main difference between #import and #include is that #import is "smart" enough to not reprocess files that have already been included in other #includes. The C Language documentation explains the main function. The NSLog() function will print the string provided to the console, along with some debugging information. In this case, we use an Objective-C string literal: @"Hello World!". In C, you would write this as "Hello World!", however, Apple's Foundation Framework adds the NSString class which provides a lot of useful functionality, and is used by NSLog. The simplest way to create an instance of NSString is like this: @">string content here". Technically, NSLog() is part of Apple's Foundation Framework and is not actually part of the Objective-C language. However, the Foundation Framework is ubiquitous throughout Objective-C programming. Since the Foundation Framework is not open-source and cannot be used outside of Apple development, there are open-source alternatives to the framework which are associated with OPENStep and GNUStep. Compiling the program Assuming we want to compile our Hello World program, which consist of a single hello.m file, the command to compile the executable is: clang -framework Foundation hello.m -o hello Then you can run it: ./hello This will output: Hello World! GoalKicker.com – Objective-C® Notes for Professionals 2 The options are: -framework: Specifies a framework to use to compile the program. Since this program uses Foundation, we include the Foundation framework. -o: This option indicate to which file we'd like to output our program. In our case hello. If not specified, the default value is a.out. GoalKicker.com – Objective-C® Notes for Professionals 3 Chapter 2: Basic Data Types Section 2.1: SEL Selectors are used as method identifiers in Objective-C. In the example below, there are two selectors. new and setName: Person* customer = [Person new]; [customer setName:@"John Doe"]; Each pair of brackets corresponds to a message send. On the first line we send a message containing the new selector to the Person class and on the second line we send a message containing the setName: selector and a string. The receiver of these messages uses the selector to look up the correct action to perform. Most of the time, message passing using the bracket syntax is sufficient, but occasionally you need to work with the selector itself. In these cases, the SEL type can be used to hold a reference to the selector. If the selector is available at compile time, you can use @selector() to get a reference to it. SEL s = @selector(setName:); And if you need to find the selector at runtime, use NSSelectorFromString. SEL s NSSelectorFromString(@"setName:"); When using NSSelectorFromString, make sure to wrap the selector name in a NSString. It is commonly used to check if a delegate implements an optional method. if ([self.myDelegate respondsToSelector:@selector(doSomething)]) { [self.myDelegate doSomething]; } Section 2.2: BOOL The BOOL type is used for boolean values in Objective-C. It has two values, YES, and NO, in contrast to the more common "true" and "false". Its behavior is straightforward and identical to the C language's. BOOL areEqual = (1 == 1); // areEqual is YES BOOL areNotEqual = !areEqual // areNotEqual is NO NSCAssert(areEqual, "Mathematics is a lie"); // Assertion passes BOOL shouldFlatterReader = YES; if (shouldFlatterReader) { NSLog(@"Only the very smartest programmers read this kind of material."); } A BOOL is a primitive, and so it cannot be stored directly in a Foundation collection. It must be wrapped in an NSNumber. Clang provides special syntax for this: NSNumber * yes = @YES; // Equivalent to [NSNumber numberWithBool:YES] GoalKicker.com – Objective-C® Notes for Professionals 4 NSNumber * no = @NO; // Equivalent to [NSNumber numberWithBool:NO] The BOOL implementation is directly based on C's, in that it is a typedef of the C99 standard type bool. The YES and NO values are defined to __objc_yes and __objc_no, respectively. These special values are compiler builtins introduced by Clang, which are translated to (BOOL)1 and (BOOL)0. If they are not available, YES and NO are defined directly as the cast-integer form. The definitions are found in the Objective-C runtime header objc.h Section 2.3: id id is the generic object pointer, an Objective-C type representing "any object". An instance of any Objective-C class can be stored in an id variable. An id and any other class type can be assigned back and forth without casting: id anonymousSurname = @"Doe"; NSString * surname = anonymousSurname; id anonymousFullName = [NSString stringWithFormat:@"%@, John", surname]; This becomes relevant when retrieving objects from a collection. The return types of methods like objectAtIndex: are id for exactly this reason. DataRecord * record = [records objectAtIndex:anIndex]; It also means that a method or function parameter typed as id can accept any object. When an object is typed as id, any known message can be passed to it: method dispatch does not depend on the compile-time type. NSString * extinctBirdMaybe = [anonymousSurname stringByAppendingString:anonymousSurname]; A message that the object does not actually respond to will still cause an exception at runtime, of course. NSDate * nope = [anonymousSurname addTimeInterval:10]; // Raises "Does not respond to selector" exception Guarding against exception. NSDate * nope; if([anonymousSurname isKindOfClass:[NSDate class]]){ nope = [anonymousSurname addTimeInterval:10]; } The id type is defined in objc.h typedef struct objc_object { Class isa; } *id; Section 2.4: IMP (implementation pointer) IMP is a C type referring to the implementation of a method, also known as an implementation pointer. It is a pointer to the start of a method implementation. Syntax: GoalKicker.com – Objective-C® Notes for Professionals 5 id (*IMP)(id, SEL, …) IMP is defined by: typedef id (*IMP)(id self,SEL _cmd,…); To access this IMP, the message “methodForSelector” can be used. Example 1: IMP ImpDoSomething = [myObject methodForSelector:@selector(doSomething)]; The method addressed by the IMP can be called by dereferencing the IMP. ImpDoSomething(myObject, @selector(doSomething)); So these calls are equal: myImpDoSomething(myObject, @selector(doSomething)); [myObject doSomething] [myObject performSelector:mySelector] [myObject performSelector:@selector(doSomething)] [myObject performSelector:NSSelectorFromString(@"doSomething")]; Example 2: SEL otherWaySelector = NSSelectorFromString(@“methodWithFirst:andSecond:andThird:"); IMP methodImplementation = [self methodForSelector:otherWaySelector]; result = methodImplementation( self, betterWaySelector, first, second, third ); NSLog(@"methodForSelector : %@", result); Here, we call [NSObject methodForSelector which returns us a pointer to the C function that actually implements the method, which we can the subsequently call directly. Section 2.5: NSInteger and NSUInteger The NSInteger is just a typedef for either an int or a long depending on the architecture. The same goes for a NSUInteger which is a typedef for the unsigned variants. If you check the NSInteger you will see the following: #if __LP64__ || (TARGET_OS_EMBEDDED && !TARGET_OS_IPHONE) || TARGET_OS_WIN32 || NS_BUILD_32_LIKE_64 typedef long NSInteger; typedef unsigned long NSUInteger; #else typedef int NSInteger; typedef unsigned int NSUInteger; #endif The difference between an signed and an unsigned int or long is that a signed int or long can contain negative GoalKicker.com – Objective-C® Notes for Professionals 6 values. The range of the int is -2 147 483 648 to 2 147 483 647 while the unsigned int has a range of 0 to 4 294 967 295. The value is doubled because the first bit isn't used anymore to say the value is negative or not. For a long and NSInteger on 64-bit architectures, the range is much wider. Most methods Apple provides are returning an NS(U)Integer over the normal int. You'll get a warning if you try to cast it to a normal int because you will lose precision if you are running on a 64-bit architecture. Not that it would matter in most cases, but it is easier to use NS(U)Integer. For example, the count method on an array will return an NSUInteger. NSNumber *iAmNumber = @0; NSInteger iAmSigned = [iAmNumber integerValue]; NSUInteger iAmUnsigned = [iAmNumber unsignedIntegerValue]; NSLog(@"%ld", iAmSigned); // The way to print a NSInteger. NSLog(@"%lu", iAmUnsigned); // The way to print a NSUInteger. Just like a BOOL, the NS(U)Integer is a primitive datatype, so you sometimes need to wrap it in a NSNumber you can use the @ before the integer to cast it like above and retrieve it using the methods below. But to cast it to NSNumber, you could also use the following methods: [NSNumber numberWithInteger:0]; [NSNumber numberWithUnsignedInteger:0]; GoalKicker.com – Objective-C® Notes for Professionals 7 Chapter 3: Enums Section 3.1: typedef enum declaration in Objective-C A enum declares a set of ordered values - the typedef just adds a handy name to this. The 1st element is 0 etc. typedef enum { Monday=1, Tuesday, Wednesday } WORKDAYS; WORKDAYS today = Monday;//value 1 Section 3.2: Converting C++ std::vector to an Objective-C Array Many C++ libraries use enums and return/receive data using vectors that contain enums. As C enums are not Objective-C objects, Objective-C collections cannot be used directly with C enums. The example below deals with this by using a combination of an NSArray and generics and a wrapper object for the array. This way, the collection can be explicit about the data type and there is no worry about possible memory leaks with C arrays Objective-C objects are used. Here is the C enum & Objective-C equivalent object: typedef enum { Error0 = 0, Error1 = 1, Error2 = 2 } MyError; @interface ErrorEnumObj : NSObject @property (nonatomic) int intValue; + (instancetype) objWithEnum:(MyError) myError; - (MyError) getEnumValue; @end @implementation ErrorEnumObj + (instancetype) objWithEnum:(MyError) error { ErrorEnumObj * obj = [ErrorEnumObj new]; obj.intValue = (int)error; return obj; } - (MyError) getEnumValue { return (MyError)self.intValue; } @end GoalKicker.com – Objective-C® Notes for Professionals 8 And here is a possible use of it in Objective-C++ (the resulting NSArray can be used in Objective-C only files as no C++ is used). class ListenerImpl : public Listener { public: ListenerImpl(Listener* listener) : _listener(listener) {} void onError(std::vector errors) override { NSMutableArray * array = [NSMutableArray new]; for (auto&& myError : errors) { [array addObject:[ErrorEnumObj objWithEnum:myError]]; } [_listener onError:array]; } private: __weak Listener* _listener; } If this kind of solution is to be used on multiple enums, the creation of the EnumObj (declaration & implementation) can be done using a macro (to create a template like solution). Section 3.3: Defining an enum Enums are defined by the following the syntax above. typedef NS_ENUM(NSUInteger, MyEnum) { MyEnumValueA, MyEnumValueB, MyEnumValueC, }; You also can set your own raw-values to the enumeration types. typedef NS_ENUM(NSUInteger, MyEnum) { MyEnumValueA = 0, MyEnumValueB = 5, MyEnumValueC = 10, }; You can also specify on the first value and all the following will use it with increment: typedef NS_ENUM(NSUInteger, MyEnum) { MyEnumValueA = 0, MyEnumValueB, MyEnumValueC, }; Variables of this enum can be created by MyEnum enumVar = MyEnumValueA. GoalKicker.com – Objective-C® Notes for Professionals 9 Chapter 4: Structs Section 4.1: Defining a Structure and Accessing Structure Members The format of the struct statement is this: struct [structure tag] { member definition; member definition; ... member definition; } [one or more structure variables]; Example: declare the ThreeFloats structure: typedef struct { float x, y, z; } ThreeFloats; @interface MyClass - (void)setThreeFloats:(ThreeFloats)threeFloats; - (ThreeFloats)threeFloats; @end Sending an instance of MyClass the message valueForKey: with the parameter @"threeFloats" will invoke the MyClass method threeFloats and return the result wrapped in an NSValue. Section 4.2: CGPoint One really good example of a struct is CGPoint; it's a simple value that represents a 2-dimensional point. It has 2 properties, x and y, and can be written as typedef struct { CGFloat x; CGFloat y; } CGPoint; If you used Objective-C for Mac or iOS app development before, you've almost certainly come across CGPoint; CGPoints hold the position of pretty much everything on screen, from views and controls to objects in a game to changes in a gradient. This means that CGPoints are used a lot. This is even more true with really performance heavy games; these games tend to have a lot of objects, and all of these objects need positions. These positions are often either CGPoints, or some other type of struct that conveys a point (such as a 3-dimensional point for 3d games). Points like CGPoint could easily be represented as objects, like @interface CGPoint { CGFloat x; CGFloat y; } ... //Point-related methods (e.g. add, isEqualToPoint, etc.) GoalKicker.com – Objective-C® Notes for Professionals 10 @property(nonatomic, assign)CGFloat x; @property(nonatomic, assign)CGFloat y; @end @implementation CGPoint @synthesize x, y; ... @end However, if CGPoint was used in this way it would take a lot longer to create and manipulate points. In smaller, faster programs this wouldn't really cause a difference, and in those cases it would be OK or maybe even better to use object points. But in large programs where points are be used a lot, using objects as points can really hurt performance, making the program slower, and also waste memory, which could force the program to crash. GoalKicker.com – Objective-C® Notes for Professionals 11 Chapter 5: Classes and Objects Section 5.1: Dierence between allocation and initialization In most object oriented languages, allocating memory for an object and initializing it is an atomic operation: // Both allocates memory and calls the constructor MyClass object = new MyClass(); In Objective-C, these are separate operations. The class methods alloc (and its historic sibling allocWithZone:) makes the Objective-C runtime reserve the required memory and clears it. Except for a few internal values, all properties and variables are set to 0/NO/nil. The object then is already "valid" but we always want to call a method to actually set up the object, which we call an initializer. These serve the same purpose as constructors in other languages. By convention, these methods start with init. From a language point of view, they are just normal methods. // Allocate memory and set all properties and variables to 0/NO/nil. MyClass *object = [MyClass alloc]; // Initialize the object. object = [object init]; // Shorthand: object = [[MyClass alloc] init]; Section 5.2: Creating classes with initialization values #import @interface Car:NSObject { NSString *CarMotorCode; NSString *CarChassisCode; } - (instancetype)initWithMotorValue:(NSString *) motorCode andChassisValue:(NSInteger)chassisCode; - (void) startCar; - (void) stopCar; @end @implementation Car - (instancetype)initWithMotorValue:(NSString *) motorCode andChassisValue:(NSInteger)chassisCode{ CarMotorCode = motorCode; CarChassisCode = chassisCode; return self; } - (void) startCar {...} - (void) stopCar {...} @end The method initWithMotorValue: type andChassisValue: type will be used to initialize the Car objects. GoalKicker.com – Objective-C® Notes for Professionals 12 Section 5.3: Specifying Generics You can enhance your own classes with generics just like NSArray or NSDictionary. @interface MyClass<__covariant T> @property (nonnull, nonatomic, strong, readonly) NSArray* allObjects; - (void) addObject:(nonnull T)obj; @end Section 5.4: Singleton Class What is a Singleton Class? A singleton class returns the same instance no matter how many times an application requests it. Unlike a regular class, A singleton object provides a global point of access to the resources of its class. When to Use Singleton Classes? Singletons are used in situations where this single point of control is desirable, such as with classes that offer some general service or resource. How to Create Singleton Classes First, create a New file and subclass it from NSObject. Name it anything, we will use CommonClass here. Xcode will now generate CommonClass.h and CommonClass.m files for you. In your CommonClass.h file: #import @interface CommonClass : NSObject { } + (CommonClass *)sharedObject; @property NSString *commonString; @end In your CommonClass.m File: #import "CommonClass.h" @implementation CommonClass + (CommonClass *)sharedObject { static CommonClass *sharedClass = nil; static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ sharedClass = [[self alloc] init]; }); return sharedClass; } - (id)init { if (self = [super init]) { self.commonString = @"this is string"; } GoalKicker.com – Objective-C® Notes for Professionals 13 return self; } @end How to Use Singleton Classes The Singleton Class that we created earlier will be accessible from anywhere in the project as long as you have imported CommonClass.h file in the relevant module. To modify and access the shared data in Singleton Class, you will have to access the shared Object of that class which can be accessed by using sharedObject method like following: [CommonClass sharedObject] To read or modify the elements in Shared Class, do the following: NSString *commonString = [[CommonClass sharedObject].commonString; //Read the string in singleton class NSString *newString = @"New String"; [CommonClass sharedObject].commonString = newString;//Modified the string in singleton class Section 5.5: The "instancetype" return type Objective-C supports a special type called `instancetype that can only be used as type returned by a method. It evaluates to the class of the receiving object. Consider the following class hierarchy: @interface Foo : NSObject - (instancetype)initWithString:(NSString *)string; @end @interface Bar : Foo @end When [[Foo alloc] initWithString:@"abc"] is called, the compiler can infer that the return type is Foo *. The Bar class derived from Foo but did not override the declaration of the initializer. Yet, thanks to instancetype, the compiler can infer that [[Bar alloc] initWithString:@"xyz"] returns a value of type Bar *. Consider the return type of -[Foo initWithString:] being Foo * instead: if you would call [[Bar alloc] initWithString:], the compiler would infer that a Foo * is returned, not a Bar * as is the intention of the developer. The instancetype solved this issue. Before the introduction of instancetype, initializers, static methods like singleton accessors and other methods that want to return an instance of the receiving class needed to return an id. The problem is that id means "an object of any type". The compiler is thus not able to detect that NSString *wrong = [[Foo alloc] initWithString:@"abc"]; is assigning to a variable with an incorrect type. Due to this issue, initializers should always use instancetype instead of id as the return value. GoalKicker.com – Objective-C® Notes for Professionals 14 Chapter 6: Inheritance Section 6.1: Car is inherited from Vehicle Consider a base class Vehicle and its derived class Car as follows: #import @interface Vehicle : NSObject { NSString *vehicleName; NSInteger vehicleModelNo; } - (id)initWithName:(NSString *)name andModel:(NSInteger)modelno; - (void)print; @end @implementation Vehicle - (id)initWithName:(NSString *)name andModel:(NSInteger)modelno{ vehicleName = name; vehicleModelNo = modelno; return self; } - (void)print{ NSLog(@"Name: %@", vehicleName); NSLog(@"Model: %ld", vehicleModelNo); } @end @interface Car : Vehicle { NSString *carCompanyName; } - (id)initWithName:(NSString *)name andModel:(NSInteger)modelno andCompanyName:(NSString *)companyname; - (void)print; @end @implementation Car - (id)initWithName:(NSString *)name andModel:(NSInteger) modelno andCompanyName: (NSString *) companyname { vehicleName = name; vehicleModelNo = modelno; carCompanyName = companyname; return self; } - (void)print { NSLog(@"Name: %@", vehicleName); GoalKicker.com – Objective-C® Notes for Professionals 15 NSLog(@"Model: %ld", vehicleModelNo); NSLog(@"Company: %@", carCompanyName); } @end int main(int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; NSLog(@"Base class Vehicle Object"); Vehicle *vehicle = [[Vehicle alloc]initWithName:@"4Wheeler" andModel:1234]; [vehicle print]; NSLog(@"Inherited Class Car Object"); Car *car = [[Car alloc]initWithName:@"S-Class" andModel:7777 andCompanyName:@"Benz"]; [car print]; [pool drain]; return 0; } When the above code is compiled and executed, it produces the following result: 2016-09-29 18:21:03.561 Inheritance[349:303] Base class Vehicle Object 2016-09-29 18:21:03.563 Inheritance[349:303] Name: 4Wheeler 2016-09-29 18:21:03.563 Inheritance[349:303] Model: 1234 2016-09-29 18:21:03.564 Inheritance[349:303] Inherited Class Car Object 2016-09-29 18:21:03.564 Inheritance[349:303] Name: S-Class 2016-09-29 18:21:03.565 Inheritance[349:303] Model: 7777 2016-09-29 18:21:03.565 Inheritance[349:303] Company: Benz GoalKicker.com – Objective-C® Notes for Professionals 16 Chapter 7: Methods Section 7.1: Class methods A class method is called on the class the method belongs to, not an instance of it. This is possible because Objective-C classes are also objects. To denote a method as a class method, change the - to a +: + (void)hello { NSLog(@"Hello World"); } Section 7.2: Pass by value parameter passing In pass by value of parameter passing to a method, actual parameter value is copied to formal parameter value. So actual parameter value will not change after returning from called function. @interface SwapClass : NSObject -(void) swap:(NSInteger)num1 andNum2:(NSInteger)num2; @end @implementation SwapClass -(void) num:(NSInteger)num1 andNum2:(NSInteger)num2{ int temp; temp = num1; num1 = num2; num2 = temp; } @end Calling the methods: NSInteger a = 10, b =20; SwapClass *swap = [[SwapClass alloc]init]; NSLog(@"Before calling swap: a=%d,b=%d",a,b); [swap num:a andNum2:b]; NSLog(@"After calling swap: a=%d,b=%d",a,b); Output: 2016-07-30 23:55:41.870 Test[5214:81162] Before calling swap: a=10,b=20 2016-07-30 23:55:41.871 Test[5214:81162] After calling swap: a=10,b=20 Section 7.3: Pass by reference parameter passing In pass by reference of parameter passing to a method, address of actual parameter is passed to formal parameter. So actual parameter value will be changed after returning from called function. @interface SwapClass : NSObject -(void) swap:(int)num1 andNum2:(int)num2; GoalKicker.com – Objective-C® Notes for Professionals 17 @end @implementation SwapClass -(void) num:(int*)num1 andNum2:(int*)num2{ int temp; temp = *num1; *num1 = *num2; *num2 = temp; } @end Calling the methods: int a = 10, b =20; SwapClass *swap = [[SwapClass alloc]init]; NSLog(@"Before calling swap: a=%d,b=%d",a,b); [swap num:&a andNum2:&b]; NSLog(@"After calling swap: a=%d,b=%d",a,b); Output: 2016-07-31 00:01:47.067 Test[5260:83491] Before calling swap: a=10,b=20 2016-07-31 00:01:47.070 Test[5260:83491] After calling swap: a=20,b=10 Section 7.4: Method parameters If you want to pass in values to a method when it is called, you use parameters: - (int)addInt:(int)intOne toInt:(int)intTwo { return intOne + intTwo; } The colon (:) separates the parameter from the method name. The parameter type goes in the parentheses (int). The parameter name goes after the parameter type. Section 7.5: Create a basic method This is how to create a basic method that logs 'Hello World" to the console: - (void)hello { NSLog(@"Hello World"); } The - at the beginning denotes this method as an instance method. The (void) denotes the return type. This method doesn't return anything, so you enter void. The 'hello' is the name of the method. Everything in the {} is the code run when the method is called. GoalKicker.com – Objective-C® Notes for Professionals 18 Section 7.6: Return values When you want to return a value from a method, you put the type you want to return in the first set of parentheses. - (NSString)returnHello { return @"Hello World"; } The value you want to return goes after the return keyword; Section 7.7: Calling methods Calling an instance method: [classInstance hello]; @interface Sample -(void)hello; // exposing the class Instance method @end @implementation Sample -(void)hello{ NSLog(@"hello"); } @end Calling an instance method on the current instance: [self hello]; @implementation Sample -(void)otherMethod{ [self hello]; } -(void)hello{ NSLog(@"hello"); } @end Calling a method that takes arguments: [classInstance addInt:1 toInt:2]; @implementation Sample -(void)add:(NSInteger)add to:(NSInteger)to NSLog(@"sum = %d",(add+to)); } @end Calling a class method: [Class hello]; @interface Sample +(void)hello; // exposing the class method @end GoalKicker.com – Objective-C® Notes for Professionals 19 @implementation Sample +(void)hello{ NSLog(@"hello"); } @end Section 7.8: Instance methods An instance method is a method that's available on a particular instance of a class, after the instance has been instantiated: MyClass *instance = [MyClass new]; [instance someInstanceMethod]; Here's how you define one: @interface MyClass : NSObject - (void)someInstanceMethod; // "-" denotes an instance method @end @implementation MyClass - (void)someInstanceMethod { NSLog(@"Whose idea was it to have a method called \"someInstanceMethod\"?"); } @end GoalKicker.com – Objective-C® Notes for Professionals 20 Chapter 8: Properties Attribute Description atomic Implicit. Enables synchronization in synthesized accessor methods. nonatomic Disables synchronization in the synthesized accessor methods. readwrite Implicit. Synthesizes getter, setter and backing ivar. readonly Synthesizes only the getter method and backing ivar, which can be assigned directly. getter=name Specifies the name of getter method, implicit is propertyName. setter=nameSpecifies the name of setter method, implicity is setPropertyName:. Colon : must be a part of the name. strong Implicit for objects under ARC. The backing ivar is synthesized using __strong, which prevents deallocation of referenced object. retain Synonym for strong. copy Same as strong, but the synthesized setter also calls -copy on the new value. Implicit, except for objects under ARC. The backing ivar is synthesized using unsafe_unretained __unsafe_unretained, which (for objects) results in dangling pointer once the referenced object deallocates. assign Synonym for unsafe_unretained. Suitable for non-object types. weak Backing ivar is synthesized using __weak, so the value will be nullified once the referenced object is deallocated. class Property accessors are synthesized as class methods, instead of instance methods. No backing storage is synthesized. nullable The property accepts nil values. Mainly used for Swift bridging. nonnull The property doesn’t accept nil values. Mainly used for Swift bridging. The property accepts nil values in setter, but never returns nil values from getter. Your null_resettable custom implementation of getter or setter must ensure this behavior. Mainly used for Swift bridging. null_unspecified Implicit. The property doesn’t specify handling of nil values. Mainly used for Swift bridging. Section 8.1: Custom getters and setters The default property getters and setters can be overridden: @interface TestClass @property NSString *someString; @end @implementation TestClass // override the setter to print a message - (void)setSomeString:(NSString *)newString { NSLog(@"Setting someString to %@", newString); // Make sure to access the ivar (default is the property name with a _ // at the beginning) because calling self.someString would call the same // method again leading to an infinite recursion _someString = newString; } - (void)doSomething { // The next line will call the setSomeString: method self.someString = @"Test"; } GoalKicker.com – Objective-C® Notes for Professionals 21 @end This can be useful to provide, for example, lazy initialization (by overriding the getter to set the initial value if it has not yet been set): - (NSString *)someString { if (_someString == nil) { _someString = [self getInitialValueForSomeString]; } return _someString; } You can also make a property that computes its value in the getter: @interface Circle : NSObject @property CGPoint origin; @property CGFloat radius; @property (readonly) CGFloat area; @end @implementation Circle - (CGFloat)area { return M_PI * pow(self.radius, 2); } @end Section 8.2: Properties that cause updates This object, Shape has a property image that depends on numberOfSides and sideWidth. If either one of them is set, than the image has to be recalculated. But recalculation is presumably long, and only needs to be done once if both properties are set, so the Shape provides a way to set both properties and only recalculate once. This is done by setting the property ivars directly. In Shape.h @interface Shape { NSUInteger numberOfSides; CGFloat sideWidth; UIImage * image; } // Initializer that takes initial values for the properties. - (instancetype)initWithNumberOfSides:(NSUInteger)numberOfSides withWidth:(CGFloat)width; // Method that allows to set both properties in once call. // This is useful if setting these properties has expensive side-effects. // Using a method to set both values at once allows you to have the side- // effect executed only once. - (void)setNumberOfSides:(NSUInteger)numberOfSides andWidth:(CGFloat)width; // Properties using default attributes. @property NSUInteger numberOfSides; @property CGFloat sideWidth; GoalKicker.com – Objective-C® Notes for Professionals 22 // Property using explicit attributes. @property(strong, readonly) UIImage * image; @end In Shape.m @implementation AnObject // The variable name of a property that is auto-generated by the compiler // defaults to being the property name prefixed with an underscore, for // example "_propertyName". You can change this default variable name using // the following statement: // @synthesize propertyName = customVariableName; - (id)initWithNumberOfSides:(NSUInteger)numberOfSides withWidth:(CGFloat)width { if ((self = [self init])) { [self setNumberOfSides:numberOfSides andWidth:width]; } return self; } - (void)setNumberOfSides:(NSUInteger)numberOfSides { _numberOfSides = numberOfSides; [self updateImage]; } - (void)setSideWidth:(CGFloat)sideWidth { _sideWidth = sideWidth; [self updateImage]; } - (void)setNumberOfSides:(NSUInteger)numberOfSides andWidth:(CGFloat)sideWidth { _numberOfSides = numberOfSides; _sideWidth = sideWidth; [self updateImage]; } // Method that does some post-processing once either of the properties has // been updated. - (void)updateImage { ... } @end When properties are assigned to (using object.property = value), the setter method setProperty: is called. This setter, even if provided by @synthesize, can be overridden, as it is in this case for numberOfSides and sideWidth. However, if you set an property's ivar directly (through property if the object is self, or object->property), it doesn't call the getter or setter, allowing you to do things like multiple property sets that only call one update or bypass side-effects caused by the setter. Section 8.3: What are properties? Here is an example class which has a couple of instance variables, without using properties: GoalKicker.com – Objective-C® Notes for Professionals 23 @interface TestClass : NSObject { NSString *_someString; int _someInt; } -(NSString *)someString; -(void)setSomeString:(NSString *)newString; -(int)someInt; -(void)setSomeInt:(NSString *)newInt; @end @implementation TestClass -(NSString *)someString { return _someString; } -(void)setSomeString:(NSString *)newString { _someString = newString; } -(int)someInt { return _someInt; } -(void)setSomeInt:(int)newInt { _someInt = newInt; } @end This is quite a lot of boilerplate code to create a simple instance variable. You have to create the instance variable & create accessor methods which do nothing except set or return the instance variable. So with Objective-C 2.0, Apple introduced properties, which auto-generate some or all of the boilerplate code. Here is the above class rewritten with properties: @interface TestClass @property NSString *someString; @property int someInt; @end @implementation testClass @end A property is an instance variable paired with auto-generated getters and setters. For a property called someString, the getter and setter are called someString and setSomeString: respectively. The name of the instance variable is, by default, the name of the property prefixed with an underscore (so the instance variable for someString is called _someString, but this can be overridden with an @synthesize directive in the @implementation section: @synthesize someString=foo; //names the instance variable "foo" @synthesize someString; //names it "someString" GoalKicker.com – Objective-C® Notes for Professionals 24 @synthesize someString=_someString; //names it "_someString"; the default if //there is no @synthesize directive Properties can be accessed by calling the getters and setters: [testObject setSomeString:@"Foo"]; NSLog(@"someInt is %d", [testObject someInt]); They can also be accessed using dot notation: testObject.someString = @"Foo"; NSLog(@"someInt is %d", testObject.someInt); GoalKicker.com – Objective-C® Notes for Professionals 25 Chapter 9: Random Integer Section 9.1: Basic Random Integer The arc4random_uniform() function is the simplest way to get high-quality random integers. As per the manual: arc4random_uniform(upper_bound) will return a uniformly distributed random number less than upper_bound. arc4random_uniform() is recommended over constructions like ''arc4random() % upper_bound'' as it avoids "modulo bias" when the upper bound is not a power of two. uint32_t randomInteger = arc4random_uniform(5); // A random integer between 0 and 4 Section 9.2: Random Integer within a Range The following code demonstrates usage of arc4random_uniform() to generate a random integer between 3 and 12: uint32_t randomIntegerWithinRange = arc4random_uniform(10) + 3; // A random integer between 3 and 12 This works to create a range because arc4random_uniform(10) returns an integer between 0 and 9. Adding 3 to this random integer produces a range between 0 + 3 and 9 + 3. GoalKicker.com – Objective-C® Notes for Professionals 26 Chapter 10: BOOL / bool / Boolean / NSCFBoolean Section 10.1: BOOL/Boolean/bool/NSCFBoolean 1. bool is a datatype defined in C99. 2. Boolean values are used in conditionals, such as if or while statements, to conditionally perform logic or repeat execution. When evaluating a conditional statement, the value 0 is considered “false”, while any other value is considered “true”. Because NULL and nil are defined as 0, conditional statements on these nonexistent values are also evaluated as “false”. 3. BOOL is an Objective-C type defined as signed char with the macros YES and NO to represent true and false From the definition in objc.h: #if (TARGET_OS_IPHONE && __LP64__) || TARGET_OS_WATCH typedef bool BOOL; #else typedef signed char BOOL; // BOOL is explicitly signed so @encode(BOOL) == "c" rather than "C" // even if -funsigned-char is used. #endif #define YES ((BOOL)1) #define NO ((BOOL)0) 4. NSCFBoolean is a private class in the NSNumber class cluster. It is a bridge to the CFBooleanRef type, which is used to wrap boolean values for Core Foundation property lists and collections. CFBoolean defines the constants kCFBooleanTrue and kCFBooleanFalse. Because CFNumberRef and CFBooleanRef are different types in Core Foundation, it makes sense that they are represented by different bridging classes in NSNumber. Section 10.2: BOOL VS Boolean BOOL Apple's Objective-C frameworks and most Objective-C/Cocoa code uses BOOL. Use BOOL in objective-C, when dealing with any CoreFoundation APIs Boolean Boolean is an old Carbon keyword , defined as an unsigned char GoalKicker.com – Objective-C® Notes for Professionals 27 Chapter 11: Continue and Break! Section 11.1: Continue and Break Statement The continue statement in Objective-C programming language works somewhat like the break statement. Instead of forcing termination, however, continue forces the next iteration of the loop to take place, skipping any code in between. For the for loop, continue statement causes the conditional test and increment portions of the loop to execute. For the while and do...while loops, continue statement causes the program control pass to the conditional tests. #import int main () { /* local variable definition */ int a = 10; /* do loop execution */ do { if( a == 15) { /* skip the iteration */ a = a + 1; continue; } NSLog(@"value of a: %d\n", a); a++; }while( a < 20 ); return 0; } Output: 2013-09-07 22:20:35.647 demo[29998] value of a: 10 2013-09-07 22:20:35.647 demo[29998] value of a: 11 2013-09-07 22:20:35.647 demo[29998] value of a: 12 2013-09-07 22:20:35.647 demo[29998] value of a: 13 2013-09-07 22:20:35.647 demo[29998] value of a: 14 2013-09-07 22:20:35.647 demo[29998] value of a: 16 2013-09-07 22:20:35.647 demo[29998] value of a: 17 2013-09-07 22:20:35.647 demo[29998] value of a: 18 2013-09-07 22:20:35.647 demo[29998] value of a: 19 Refer to this link for more information. GoalKicker.com – Objective-C® Notes for Professionals 28 Chapter 12: Key Value Coding / Key Value Observing Section 12.1: Most Common Real Life Key Value Coding Example Key Value Coding is integrated into NSObject using NSKeyValueCoding protocol. What this means? It means that any id object is capable of calling valueForKey method and its various variants like valueForKeyPath etc. ' It also means that any id object can invoke setValue method and its various variants too. Example: id obj = [[MyClass alloc] init]; id value = [obj valueForKey:@"myNumber"]; int myNumberAsInt = [value intValue]; myNumberAsInt = 53; [obj setValue:@(myNumberAsInt) forKey:@"myNumber"]; Exceptions: Above example assumes that MyClass has an NSNumber Property called myNumber. If myNumber does not appear in MyClass interface definition, an NSUndefinedKeyException can be raised at possibly both lines 2 and 5 - popularly known as: this class is not key value coding-compliant for the key myNumber. Why this is SO powerful: You can write code that can access properties of a class dynamically, without needing interface for that class. This means that a table view can display values from any properties of an NSObject derived object, provided its property names are supplied dynamically at runtime. In the example above, the code can as well work without MyClass being available and id type obj being available to calling code. Section 12.2: Querying KVC Data if ([[dataObject objectForKey:@"yourVariable"] isEqualToString:"Hello World"]) { return YES; } else { return NO; } You can query values stored using KVC quickly and easily, without needing to retrieve or cast these as local variables. GoalKicker.com – Objective-C® Notes for Professionals 29 Section 12.3: Collection Operators Collection Operators can be used in a KVC key path to perform an operation on a “collection-type” property (i.e. NSArray, NSSet and similar). For example, a common operation to perform is to count the objects in a collection. To achieve this, you use the @count collection operator: self.array = @[@5, @4, @3, @2, @1]; NSNumber *count = [self.array valueForKeyPath:@"@count"]; NSNumber *countAlt = [self valueForKeyPath:@"array.@count"]; // count == countAlt == 5 While this is completely redundant here (we could have just accessed the count property), it can be useful on occasion, though it is rarely necessary. There are, however, some collection operators that are much more useful, namely @max, @min, @sum, @avg and the @unionOf family. It is important to note that these operators also require a separate key path following the operator to function correctly. Here's a list of them and the type of data they work with: Operator Data Type @count (none) @max NSNumber, NSDate, int (and related), etc. @min NSNumber, NSDate, int (and related), etc. @sum NSNumber, int (and related), double (and related), etc. @avg NSNumber, int (and related), double (and related), etc. @unionOfObjects NSArray, NSSet, etc. @distinctUnionOfObjects NSArray, NSSet, etc. @unionOfArrays NSArray @distinctUnionOfArrays NSArray @distinctUnionOfSets NSSet @max and @min will return the highest or lowest value, respectively, of a property of objects in the collection. For example, look at the following code: // “Point” class used in our collection @interface Point : NSObject @property NSInteger x, y; + (instancetype)pointWithX:(NSInteger)x y:(NSInteger)y; @end ... self.points = @[[Point pointWithX:0 y:0], [Point pointWithX:1 y:-1], [Point pointWithX:5 y:-6], [Point pointWithX:3 y:0], [Point pointWithX:8 y:-4], ]; NSNumber *maxX = [self valueForKeyPath:@"[email protected]"]; NSNumber *minX = [self valueForKeyPath:@"[email protected]"]; NSNumber *maxY = [self valueForKeyPath:@"[email protected]"]; NSNumber *minY = [self valueForKeyPath:@"[email protected]"]; GoalKicker.com – Objective-C® Notes for Professionals 30 NSArray *boundsOfAllPoints = @[maxX, minX, maxY, minY]; ... In just a 4 lines of code and pure Foundation, with the power of Key-Value Coding collection operators we were able to extract a rectangle that encapsulates all of the points in our array. It is important to note that these comparisons are made by invoking the compare: method on the objects, so if you ever want to make your own class compatible with these operators, you must implement this method. @sum will, as you can probably guess, add up all the values of a property. @interface Expense : NSObject @property NSNumber *price; + (instancetype)expenseWithPrice:(NSNumber *)price; @end ... self.expenses = @[[Expense expenseWithPrice:@1.50], [Expense expenseWithPrice:@9.99], [Expense expenseWithPrice:@2.78], [Expense expenseWithPrice:@9.99], [Expense expenseWithPrice:@24.95] ]; NSNumber *totalExpenses = [self valueForKeyPath:@"[email protected]"]; Here, we used @sum to find the total price of all the expenses in the array. If we instead wanted to find the average price we're paying for each expense, we can use @avg: NSNumber *averagePrice = [self valueForKeyPath:@"[email protected]"]; Finally, there's the @unionOf family. There are five different operators in this family, but they all work mostly the same, with only small differences between each. First, there's @unionOfObjects which will return an array of the properties of objects in an array: // See "expenses" array above NSArray *allPrices = [self valueForKeyPath: @"[email protected]"]; // Equal to @[ @1.50, @9.99, @2.78, @9.99, @24.95 ] @distinctUnionOfObjects functions the same as @unionOfObjects, but it removes duplicates: NSArray *differentPrices = [self valueForKeyPath: @"[email protected]"]; // Equal to @[ @1.50, @9.99, @2.78, @24.95 ] And finally, the last 3 operators in the @unionOf family will go one step deeper and return an array of values found for a property contained inside dually-nested arrays: GoalKicker.com – Objective-C® Notes for Professionals 31 NSArray*> *arrayOfArrays = @[ @[ [Expense expenseWithPrice:@19.99], [Expense expenseWithPrice:@14.95], [Expense expenseWithPrice:@4.50], [Expense expenseWithPrice:@19.99] ], @[ [Expense expenseWithPrice:@3.75], [Expense expenseWithPrice:@14.95] ] ]; // @unionOfArrays NSArray allPrices = [arrayOfArrays valueForKeyPath: @"@unionOfArrays.price"]; // Equal to @[ @19.99, @14.95, @4.50, @19.99, @3.75, @14.95 ]; // @distinctUnionOfArrays NSArray allPrices = [arrayOfArrays valueForKeyPath: @"@distinctUnionOfArrays.price"]; // Equal to @[ @19.99, @14.95, @4.50, @3.75 ]; The one missing from this example is @distinctUnionOfSets, however this functions exactly the same as @distinctUnionOfArrays, but works with and returns NSSets instead (there is no non-distinct version because in a set, every object must be distinct anyway). And that's it! Collection operators can be really powerful if used correctly, and can help to avoid having to loop through stuff unnecessarily. One last note: you can also use the standard collection operators on arrays of NSNumbers (without additional property access). To do this, you access the self pseudo-property that just returns the object: NSArray *numbers = @[@0, @1, @5, @27, @1337, @2048]; NSNumber *largest = [numbers valueForKeyPath:@"@max.self"]; NSNumber *smallest = [numbers valueForKeyPath:@"@min.self"]; NSNumber *total = [numbers valueForKeyPath:@"@sum.self"]; NSNumber *average = [numbers valueForKeyPath:@"@avg.self"]; Section 12.4: Key Value Observing Setting up key value observing. In this case, we want to observe the contentOffset on an object that our observer owns // // Class to observe // @interface XYZScrollView: NSObject @property (nonatomic, assign) CGPoint contentOffset; @end @implementation XYZScrollView @end // // Class that will observe changes GoalKicker.com – Objective-C® Notes for Professionals 32 // @interface XYZObserver: NSObject @property (nonatomic, strong) XYZScrollView *scrollView; @end @implementation XYZObserver // simple way to create a KVO context static void *XYZObserverContext = &XYZObserverContext; // Helper method to add self as an observer to // the scrollView's contentOffset property - (void)addObserver { // NSKeyValueObservingOptions // // - NSKeyValueObservingOptionNew // - NSKeyValueObservingOptionOld // - NSKeyValueObservingOptionInitial // - NSKeyValueObservingOptionPrior // // can be combined: // (NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld) NSString *keyPath = NSStringFromSelector(@selector(contentOffset)); NSKeyValueObservingOptions options = NSKeyValueObservingOptionNew; [self.scrollView addObserver: self forKeyPath: keyPath options: options context: XYZObserverContext]; } - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { if (context == XYZObserverContext) { // check the context // check the keyPath to see if it's any of the desired keyPath's. // You can observe multiple keyPath's if ([keyPath isEqualToString: NSStringFromSelector(@selector(contentOffset))]) { // change dictionary keys: // - NSKeyValueChangeKindKey // - NSKeyValueChangeNewKey // - NSKeyValueChangeOldKey // - NSKeyValueChangeIndexesKey // - NSKeyValueChangeNotificationIsPriorKey // the change dictionary here for a CGPoint observation will // return an NSPoint, so we can take the CGPointValue of it. CGPoint point = [change[NSKeyValueChangeNewKey] CGPointValue]; // handle point } } else { // if the context doesn't match our current object's context // we want to pass the observation parameters to super [super observeValueForKeyPath: keyPath GoalKicker.com – Objective-C® Notes for Professionals 33 ofObject: object change: change context: context]; } } // The program can crash if an object is not removed as observer // before it is dealloc'd // // Helper method to remove self as an observer of the scrollView's // contentOffset property - (void)removeObserver { NSString *keyPath = NSStringFromSelector(@selector(contentOffset)); [self.scrollView removeObserver: self forKeyPath: keyPath]; } @end GoalKicker.com – Objective-C® Notes for Professionals 34 Chapter 13: NSString The NSString class is a part of Foundation framework to work with strings (series of characters). It also includes methods for comparing, searching and modifying strings. Section 13.1: Encoding and Decoding // decode NSString *string = [[NSString alloc] initWithData:utf8Data encoding:NSUTF8StringEncoding]; // encode NSData *utf8Data = [string dataUsingEncoding:NSUTF8StringEncoding]; Some supported encodings are: NSASCIIStringEncoding NSUTF8StringEncoding NSUTF16StringEncoding (== NSUnicodeStringEncoding) Note that utf8Data.bytes does not include a terminating null character, which is necessary for C strings. If you need a C string, use UTF8String: const char *cString = [string UTF8String]; printf("%s", cString); Section 13.2: String Length NSString has a length property to get the number of characters. NSString *string = @"example"; NSUInteger length = string.length; // length equals 7 As in the Splitting Example, keep in mind that NSString uses UTF-16 to represent characters. The length is actually just the number of UTF-16 code units. This can differ from what the user perceives as characters. Here are some cases that might be surprising: @"é".length == 1 // LATIN SMALL LETTER E WITH ACUTE (U+00E9) @"é".length == 2 // LATIN SMALL LETTER E (U+0065) + COMBINING ACUTE ACCENT (U+0301) @"❤".length == 2 // HEAVY BLACK HEART (U+2764) + VARIATION SELECTOR-16 (U+FE0F) @"".length == 4 // REGIONAL INDICATOR SYMBOL LETTER I (U+1F1EE) + REGIONAL INDICATOR SYMBOL LETTER T (U+1F1F9) In order to get the number of user-perceived characters, known technically as "grapheme clusters", you must iterate over the string with -enumerateSubstringsInRange:options:usingBlock: and keep a count. This is demonstrated in an answer by Nikolai Ruhe on Stack Overflow. Section 13.3: Comparing Strings Strings are compared for equality using isEqualToString: The == operator just tests for object identity and does not compare the logical values of objects, so it can't be used: GoalKicker.com – Objective-C® Notes for Professionals 35 NSString *stringOne = @"example"; NSString *stringTwo = [stringOne mutableCopy]; BOOL objectsAreIdentical = (stringOne == stringTwo); // NO BOOL stringsAreEqual = [stringOne isEqualToString:stringTwo]; // YES The expression (stringOne == stringTwo) tests to see if the memory addresses of the two strings are the same, which is usually not what we want. If the string variables can be nil you have to take care about this case as well: BOOL equalValues = stringOne == stringTwo || [stringOne isEqualToString:stringTwo]; This condition returns YES when strings have equal values or both are nil. To order two strings alphabetically, use compare:. NSComparisonResult result = [firstString compare:secondString]; NSComparisonResult can be: NSOrderedAscending: The first string comes before the second string. NSOrderedSame: The strings are equal. NSOrderedDescending: The second string comes before the first string. To compare two strings equality, use isEqualToString:. BOOL result = [firstString isEqualToString:secondString]; To compare with the empty string (@""), better use length. BOOL result = string.length == 0; Section 13.4: Splitting You can split a string into an array of parts, divided by a separator character. NSString * yourString = @"Stack,Exchange,Network"; NSArray * yourWords = [yourString componentsSeparatedByString:@","]; // Output: @[@"Stack", @"Exchange", @"Network"] If you need to split on a set of several different delimiters, use -[NSString componentsSeparatedByCharactersInSet:]. NSString * yourString = @"Stack Overflow+Documentation/Objective-C"; NSArray * yourWords = [yourString componentsSeparatedByCharactersInSet: [NSCharacterSet characterSetWithCharactersInString:@"+/"]]; // Output: @[@"Stack Overflow", @"Documentation", @"Objective-C"]` If you need to break a string into its individual characters, loop over the length of the string and convert each character into a new string. NSMutableArray * characters = [[NSMutableArray alloc] initWithCapacity:[yourString length]]; for (int i = 0; i < [myString length]; i++) { [characters addObject: [NSString stringWithFormat:@"%C", GoalKicker.com – Objective-C® Notes for Professionals 36 [yourString characterAtIndex:i]]; } As in the Length Example, keep in mind that a "character" here is a UTF-16 code unit, not necessarily what the user sees as a character. If you use this loop with @"", you'll see that it's split into four pieces. In order to get a list of the user-perceived characters, use -enumerateSubstringsInRange:options:usingBlock:. NSMutableArray * characters = [NSMutableArray array]; [yourString enumerateSubstringsInRange:(NSRange){0, [yourString length]} options:NSStringEnumerationByComposedCharacterSequences usingBlock:^(NSString * substring, NSRange r, NSRange s, BOOL * b){ [characters addObject:substring]; }]; This preserves grapheme clusters like the Italian flag as a single substring. Section 13.5: Searching for a Substring To search if a String contains a substring, do the following: NSString *myString = @"This is for checking substrings"; NSString *subString = @"checking"; BOOL doesContainSubstring = [myString containsString:subString]; // YES If targeting iOS 7 or OS X 10.9 (or earlier): BOOL doesContainSubstring = ([myString rangeOfString:subString].location != NSNotFound); // YES Section 13.6: Creation Simple: NSString *newString = @"My String"; From multiple strings: NSString *stringOne = @"Hello"; NSString *stringTwo = @"world"; NSString *newString = [NSString stringWithFormat:@"My message: %@ %@", stringOne, stringTwo]; Using Mutable String NSString *stringOne = @"Hello"; NSString *stringTwo = @"World"; NSMutableString *mutableString = [NSMutableString new]; [mutableString appendString:stringOne]; [mutableString appendString:stringTwo]; From NSData: When initializing from NSData, an explicit encoding must be provided as NSString is not able to guess how characters are represented in the raw data stream. The most common encoding nowadays is UTF-8, which is even a GoalKicker.com – Objective-C® Notes for Professionals 37 requirement for certain data like JSON. Avoid using +[NSString stringWithUTF8String:] since it expects an explicitly NULL-terminated C-string, which - [NSData bytes] does not provide. NSString *newString = [[NSString alloc] initWithData:myData encoding:NSUTF8StringEncoding]; From NSArray: NSArray *myArray = [NSArray arrayWithObjects:@"Apple", @"Banana", @"Strawberry", @"Kiwi", nil]; NSString *newString = [myArray componentsJoinedByString:@" "]; Section 13.7: Changing Case To convert a String to uppercase, use uppercaseString: NSString *myString = @"Emphasize this"; NSLog(@"%@", [myString uppercaseString]; // @"EMPHASIZE THIS" To convert a String to lowercase, use lowercaseString: NSString *myString = @"NORMALIZE this"; NSLog(@"%@", [myString lowercaseString]; // @"normalize this" To capitalize the first letter character of each word in a string, use capitalizedString: NSString *myString = @"firstname lastname"; NSLog(@"%@", [myString capitalizedString]); // @"Firstname Lastname" Section 13.8: Removing Leading and Trailing Whitespace NSString *someString = @" Objective-C Language \n"; NSString *trimmedString = [someString stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; //Output will be - "Objective-C Language" Method stringByTrimmingCharactersInSet returns a new string made by removing from both ends of the String characters contained in a given character set. We can also just remove only whitespace or newline // Removing only WhiteSpace NSString *trimmedWhiteSpace = [someString stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]; //Output will be - "Objective-C Language \n" // Removing only NewLine NSString *trimmedNewLine = [someString stringByTrimmingCharactersInSet:[NSCharacterSet newlineCharacterSet]]; //Output will be - " Objective-C Language " Section 13.9: Joining an Array of Strings To combine an NSArray of NSString into a new NSString: GoalKicker.com – Objective-C® Notes for Professionals 38 NSArray *yourWords = @[@"Objective-C", @"is", @"just", @"awesome"]; NSString *sentence = [yourWords componentsJoinedByString:@" "]; // Sentence is now: @"Objective-C is just awesome" Section 13.10: Formatting The NSString formatting supports all the format strings available on the printf ANSI-C function. The only addition made by the language is the %@ symbol used for formatting all the Objective-C objects. It is possible to format integers int myAge = 21; NSString *formattedAge = [NSString stringWithFormat:@"I am %d years old", my_age]; Or any object subclassed from NSObject NSDate *now = [NSDate date]; NSString *formattedDate = [NSString stringWithFormat:@"The time right now is: %@", now]; For a complete list of Format Specifiers, please see: Objective-C, Format Specifiers, Syntax Section 13.11: Working with C Strings To convert NSString to const char use -[NSString UTF8String]: NSString *myNSString = @"Some string"; const char *cString = [myNSString UTF8String]; You could also use -[NSString cStringUsingEncoding:] if your string is encoded with something other than UTF-8. For the reverse path use -[NSString stringWithUTF8String:]: const *char cString = "Some string"; NSString *myNSString = [NSString stringWithUTF8String:cString]; myNSString = @(cString); // Equivalent to the above. Once you have the const char *, you can work with it similarly to an array of chars: printf("%c\n", cString[5]); If you want to modify the string, make a copy: char *cpy = calloc(strlen(cString)+1, 1); strncpy(cpy, cString, strlen(cString)); // Do stuff with cpy free(cpy); Section 13.12: Reversing a NSString Objective-C // myString is "hi" NSMutableString *reversedString = [NSMutableString string]; NSInteger charIndex = [myString length]; while (charIndex > 0) { GoalKicker.com – Objective-C® Notes for Professionals 39 charIndex--; NSRange subStrRange = NSMakeRange(charIndex, 1); [reversedString appendString:[myString substringWithRange:subStrRange]]; } NSLog(@"%@", reversedString); // outputs "ih" GoalKicker.com – Objective-C® Notes for Professionals 40 Chapter 14: NSArray Section 14.1: Creating Arrays Creating immutable arrays: NSArray *myColors = [NSArray arrayWithObjects: @"Red", @"Green", @"Blue", @"Yellow", nil]; // Using the array literal syntax: NSArray *myColors = @[@"Red", @"Green", @"Blue", @"Yellow"]; For mutable arrays, see NSMutableArray. Section 14.2: Accessing elements NSArray *myColors = @[@"Red", @"Green", @"Blue", @"Yellow"]; // Preceding is the preferred equivalent to [NSArray arrayWithObjects:...] Getting a single item The objectAtIndex: method provides a single object. The first object in an NSArray is index 0. Since an NSArray can be homogenous (holding different types of objects), the return type is id ("any object"). (An id can be assigned to a variable of any other object type.) Importantly, NSArrays can only contain objects. They cannot contain values like int. NSUInteger idx = 2; NSString *color = [myColors objectAtIndex:idx]; // color now points to the string @"Green" Clang provides a better subscript syntax as part of its array literals functionality: NSString *color = myColors[idx]; Both of these throw an exception if the passed index is less than 0 or greater than count - 1. First and Last Item NSString *firstColor = myColors.firstObject; NSString *lastColor = myColors.lastObject; The firstObject and lastObject are computed properties and return nil rather than crashing for empty arrays. For single element arrays they return the same object. Although, the firstObject method was not introduced to NSArray until iOS 4.0. NSArray *empty = @[] id notAnObject = empty.firstObject; // Returns `nil` id kaboom = empty[0]; // Crashes; index out of bounds Section 14.3: Using Generics For added safety we can define the type of object that the array contains: NSArray *colors = @[@"Red", @"Green", @"Blue", @"Yellow"]; NSMutableArray *myColors = [NSMutableArray arrayWithArray:colors]; GoalKicker.com – Objective-C® Notes for Professionals 41 [myColors addObject:@"Orange"]; // OK [myColors addObject:[UIColor purpleColor]]; // "Incompatible pointer type" warning It should be noted that this is checked during compilation time only. Section 14.4: Reverse an Array NSArray *reversedArray = [myArray.reverseObjectEnumerator allObjects]; Section 14.5: Converting between Sets and Arrays NSSet *set = [NSSet set]; NSArray *array = [NSArray array]; NSArray *fromSet = [set allObjects]; NSSet *fromArray = [NSSet setWithArray:array]; Section 14.6: Converting NSArray to NSMutableArray to allow modification NSArray *myColors = [NSArray arrayWithObjects: @"Red", @"Green", @"Blue", @"Yellow", nil]; // Convert myColors to mutable NSMutableArray *myColorsMutable = [myColors mutableCopy]; Section 14.7: Looping through NSArray *myColors = @[@"Red", @"Green", @"Blue", @"Yellow"]; // Fast enumeration // myColors cannot be modified inside the loop for (NSString *color in myColors) { NSLog(@"Element %@", color); } // Using indices for (NSUInteger i = 0; i < myColors.count; i++) { NSLog(@"Element %d = %@", i, myColors[i]); } // Using block enumeration [myColors enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL * stop) { NSLog(@"Element %d = %@", idx, obj); // To abort use: *stop = YES }]; // Using block enumeration with options [myColors enumerateObjectsWithOptions:NSEnumerationReverse usingBlock:^(id obj, NSUInteger idx, BOOL * stop) { NSLog(@"Element %d = %@", idx, obj); }]; GoalKicker.com – Objective-C® Notes for Professionals 42 Section 14.8: Enumerating using blocks NSArray *myColors = @[@"Red", @"Green", @"Blue", @"Yellow"]; [myColors enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) { NSLog(@"enumerating object %@ at index %lu", obj, idx); }]; By setting the stop parameter to YES you can indicate that further enumeration is not needed. to do this simply set &stop = YES. NSEnumerationOptions You can enumerate the array in reverse and / or concurrently : [myColors enumerateObjectsWithOptions:NSEnumerationConcurrent | NSEnumerationReverse usingBlock:^(id obj, NSUInteger idx, BOOL *stop) { NSLog(@"enumerating object %@ at index %lu", obj, idx); }]; Enumerating subset of array NSIndexSet *indexSet = [NSIndexSet indexSetWithIndexesInRange:NSMakeRange(1, 1)]; [myColors enumerateObjectsAtIndexes:indexSet options:kNilOptions usingBlock:^(id obj, NSUInteger idx, BOOL *stop) { NSLog(@"enumerating object %@ at index %lu", obj, idx); }]; Section 14.9: Comparing arrays Arrays can be compared for equality with the aptly named isEqualToArray: method, which returns YES when both arrays have the same number of elements and every pair pass an isEqual: comparison. NSArray *germanMakes = @[@"Mercedes-Benz", @"BMW", @"Porsche", @"Opel", @"Volkswagen", @"Audi"]; NSArray *sameGermanMakes = [NSArray arrayWithObjects:@"Mercedes-Benz", @"BMW", @"Porsche", @"Opel", @"Volkswagen", @"Audi", nil]; if ([germanMakes isEqualToArray:sameGermanMakes]) { NSLog(@"Oh good, literal arrays are the same as NSArrays"); } The important thing is every pair must pass the isEqual: test. For custom objects this method should be implemented. It exists in the NSObject protocol. Section 14.10: Filtering Arrays With Predicates NSArray *array = [NSArray arrayWithObjects:@"Nick", @"Ben", @"Adam", @"Melissa", nil]; NSPredicate *aPredicate = [NSPredicate predicateWithFormat:@"SELF beginswith[c] 'a'"]; NSArray *beginWithA = [array filteredArrayUsingPredicate:bPredicate]; // beginWithA contains { @"Adam" }. NSPredicate *ePredicate = [NSPredicate predicateWithFormat:@"SELF contains[c] 'e'"]; [array filterUsingPredicate:ePredicate]; // array now contains { @"Ben", @"Melissa" } GoalKicker.com – Objective-C® Notes for Professionals 43 More about NSPredicate: Apple doc : NSPredicate Section 14.11: Sorting array with custom objects Compare method Either you implement a compare-method for your object: - (NSComparisonResult)compare:(Person *)otherObject { return [self.birthDate compare:otherObject.birthDate]; } NSArray *sortedArray = [drinkDetails sortedArrayUsingSelector:@selector(compare:)]; NSSortDescriptor NSSortDescriptor *sortDescriptor; sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"birthDate" ascending:YES]; NSArray *sortDescriptors = [NSArray arrayWithObject:sortDescriptor]; NSArray *sortedArray = [drinkDetails sortedArrayUsingDescriptors:sortDescriptors]; You can easily sort by multiple keys by adding more than one to the array. Using custom comparator-methods is possible as well. Have a look at the documentation. Blocks NSArray *sortedArray; sortedArray = [drinkDetails sortedArrayUsingComparator:^NSComparisonResult(id a, id b) { NSDate *first = [(Person*)a birthDate]; NSDate *second = [(Person*)b birthDate]; return [first compare:second]; }]; Performance The -compare: and block-based methods will be quite a bit faster, in general, than using NSSortDescriptor as the latter relies on KVC. The primary advantage of the NSSortDescriptor method is that it provides a way to define your sort order using data, rather than code, which makes it easy to e.g. set things up so users can sort an NSTableView by clicking on the header row. Section 14.12: Sorting Arrays The most flexible ways to sort an array is with the sortedArrayUsingComparator: method. This accepts an ^NSComparisonResult(id obj1, id obj2) block. Return Value Description NSOrderedAscending obj1 comes before obj2 NSOrderedSame obj1 and obj2 have no order NSOrderedDescending obj1 comes after obj2 Example: NSArray *categoryArray = @[@"Apps", @"Music", @"Songs", GoalKicker.com – Objective-C® Notes for Professionals 44 @"iTunes", @"Books", @"Videos"]; NSArray *sortedArray = [categoryArray sortedArrayUsingComparator: ^NSComparisonResult(id obj1, id obj2) { if ([obj1 length] < [obj2 length]) { return NSOrderedAscending; } else if ([obj1 length] > [obj2 length]) { return NSOrderedDescending; } else { return NSOrderedSame; } }]; NSLog(@"%@", sortedArray); Section 14.13: Filter NSArray and NSMutableArray NSMutableArray *array = [NSMutableArray arrayWithObjects:@"Ken", @"Tim", @"Chris", @"Steve",@"Charlie",@"Melissa", nil]; NSPredicate *bPredicate = [NSPredicate predicateWithFormat:@"SELF beginswith[c] 'c'"]; NSArray *beginWithB = [array filteredArrayUsingPredicate:bPredicate]; // beginWith "C" contains { @"Chris", @"Charlie" }. NSPredicate *sPredicate = [NSPredicate predicateWithFormat:@"SELF contains[c] 'a'"]; [array filterUsingPredicate:sPredicate]; // array now contains { @"Charlie", @"Melissa" } Section 14.14: Add objects to NSArray NSArray *a = @[@1]; a = [a arrayByAddingObject:@2]; a = [a arrayByAddingObjectsFromArray:@[@3, @4, @5]]; These methods are optimized to recreate the new array very efficiently, usually without having to destroy the original array or even allocate more memory. Section 14.15: Finding out the Number of Elements in an Array NSArray *myColors = [NSArray arrayWithObjects: @"Red", @"Green", @"Blue", @"Yellow", nil]; NSLog (@"Number of elements in array = %lu", [myColors count]); Section 14.16: Creating NSArray instances NSArray *array1 = [NSArray arrayWithObjects:@"one", @"two", @"three", nil]; NSArray *array2 = @[@"one", @"two", @"three"]; GoalKicker.com – Objective-C® Notes for Professionals 45 Chapter 15: NSMutableArray Section 15.1: Sorting Arrays NSMutableArray *myColors = [NSMutableArray arrayWithObjects: @"red", @"green", @"blue", @"yellow", nil]; NSArray *sortedArray; sortedArray = [myColors sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)]; Section 15.2: Creating an NSMutableArray NSMutableArray can be initialized as an empty array like this: NSMutableArray *array = [[NSMutableArray alloc] init]; // or NSMutableArray *array2 = @[].mutableCopy; // or NSMutableArray *array3 = [NSMutableArray array]; NSMutableArray can be initialized with another array like this: NSMutableArray *array4 = [[NSMutableArray alloc] initWithArray:anotherArray]; // or NSMutableArray *array5 = anotherArray.mutableCopy; Section 15.3: Adding elements NSMutableArray *myColors; myColors = [NSMutableArray arrayWithObjects: @"Red", @"Green", @"Blue", @"Yellow", nil]; [myColors addObject: @"Indigo"]; [myColors addObject: @"Violet"]; //Add objects from an NSArray NSArray *myArray = @[@"Purple",@"Orange"]; [myColors addObjectsFromArray:myArray]; Section 15.4: Insert Elements NSMutableArray *myColors; int i; int count; myColors = [NSMutableArray arrayWithObjects: @"Red", @"Green", @"Blue", @"Yellow", nil]; [myColors insertObject: @"Indigo" atIndex: 1]; [myColors insertObject: @"Violet" atIndex: 3]; Section 15.5: Deleting Elements Remove at specific index: [myColors removeObjectAtIndex: 3]; Remove the first instance of a specific object: [myColors removeObject: @"Red"]; GoalKicker.com – Objective-C® Notes for Professionals 46 Remove all instances of a specific object: [myColors removeObjectIdenticalTo: @"Red"]; Remove all objects: [myColors removeAllObjects]; Remove last object: [myColors removeLastObject]; Section 15.6: Move object to another index Move Blue to the beginning of the array: NSMutableArray *myColors = [NSMutableArray arrayWithObjects: @"Red", @"Green", @"Blue", @"Yellow", nil]; NSUInteger fromIndex = 2; NSUInteger toIndex = 0; id blue = [[[self.array objectAtIndex:fromIndex] retain] autorelease]; [self.array removeObjectAtIndex:fromIndex]; [self.array insertObject:blue atIndex:toIndex]; myColors is now [@"Blue", @"Red", @"Green", @"Yellow"]. Section 15.7: Filtering Array content with Predicate Using filterUsingPredicate: This Evaluates a given predicate against the arrays content and return objects that match. Example: NSMutableArray *array = [NSMutableArray array]; [array setArray:@[@"iOS",@"macOS",@"tvOS"]]; NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF beginswith[c] 'i'"]; NSArray *resultArray = [array filteredArrayUsingPredicate:predicate]; NSLog(@"%@",resultArray); GoalKicker.com – Objective-C® Notes for Professionals 47 Chapter 16: NSDictionary Section 16.1: Create NSDictionary *dict = [[NSDictionary alloc] initWithObjectsAndKeys:@"value1", @"key1", @"value2", @"key2", nil]; or NSArray *keys = [NSArray arrayWithObjects:@"key1", @"key2", nil]; NSArray *objects = [NSArray arrayWithObjects:@"value1", @"value2", nil]; NSDictionary *dictionary = [NSDictionary dictionaryWithObjects:objects forKeys:keys]; or using appropriate literal syntax NSDictionary *dict = @{@"key": @"value", @"nextKey": @"nextValue"}; Section 16.2: Fast Enumeration NSDictionary can be enumerated using fast enumeration, just like other collection types: NSDictionary stockSymbolsDictionary = @{ @"AAPL": @"Apple", @"GOOGL": @"Alphabet", @"MSFT": @"Microsoft", @"AMZN": @"Amazon" }; for (id key in stockSymbolsDictionary) { id value = dictionary[key]; NSLog(@"Key: %@, Value: %@", key, value); } Because NSDictionary is inherently unordered, the order of keys that in the for loop is not guaranteed. Section 16.3: Creating using literals NSDictionary *inventory = @{ @"Mercedes-Benz SLK250" : @(13), @"BMW M3 Coupe" : @(self.BMWM3CoupeInventory.count), @"Last Updated" : @"Jul 21, 2016", @"Next Update" : self.nextInventoryUpdateString }; Section 16.4: Creating using dictionaryWithObjectsAndKeys: NSDictionary *inventory = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithInt:13], @"Mercedes-Benz SLK250", [NSNumber numberWithInt:22], @"Mercedes-Benz E350", [NSNumber numberWithInt:19], @"BMW M3 Coupe", [NSNumber numberWithInt:16], @"BMW X6", nil]; GoalKicker.com – Objective-C® Notes for Professionals 48 nil must be passed as the last parameter as a sentinel signifying the end. It's important to remember that when instantiating dictionaries this way the values go first and the keys second. In the example above the strings are the keys and the numbers are the values. The method's name reflects this too: dictionaryWithObjectsAndKeys. While this is not incorrect, the more modern way of instantiating dictionaries (with literals) is preferred. Section 16.5: NSDictionary to NSArray NSDictionary *myDictionary = [[NSDictionary alloc] initWithObjectsAndKeys:@"value1", @"key1", @"value2", @"key2", nil]; NSArray *copiedArray = myDictionary.copy; Get keys: NSArray *keys = [myDictionary allKeys]; Get values: NSArray *values = [myDictionary allValues]; Section 16.6: NSDictionary to NSData NSDictionary *myDictionary = [[NSDictionary alloc] initWithObjectsAndKeys:@"value1", @"key1", @"value2", @"key2", nil]; NSData *myData = [NSKeyedArchiver archivedDataWithRootObject:myDictionary]; Reserve path: NSDictionary *myDictionary = (NSDictionary*) [NSKeyedUnarchiver unarchiveObjectWithData:myData]; Section 16.7: NSDictionary to JSON NSDictionary *myDictionary = [[NSDictionary alloc] initWithObjectsAndKeys:@"value1", @"key1", @"value2", @"key2", nil]; NSMutableDictionary *mutableDictionary = [myDictionary mutableCopy]; NSData *data = [NSJSONSerialization dataWithJSONObject:myDictionary options:NSJSONWritingPrettyPrinted error:nil]; NSString *jsonString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]; Section 16.8: Creating using plists NSString *pathToPlist = [[NSBundle mainBundle] pathForResource:@"plistName" ofType:@"plist"]; NSDictionary *plistDict = [[NSDictionary alloc] initWithContentsOfFile:pathToPlist]; Section 16.9: Setting a Value in NSDictionary There are multiple ways to set a key's object in an NSDictionary, corresponding to the ways you get a value. For instance, to add a Lamborghini to a list of cars Standard GoalKicker.com – Objective-C® Notes for Professionals 49 [cars setObject:lamborghini forKey:@"Lamborghini"]; Just like any other object, call the method of NSDictionary that sets an object of a key, objectForKey:. Be careful not to confuse this with setValue:forKey:; that's for a completely different thing, Key Value Coding Shorthand cars[@"Lamborghini"] = lamborghini; This is the syntax that you use for dictionaries in most other languages, such as C#, Java, and JavaScript. It's much more convenient than the standard syntax, and arguably more readable (especially if you code in these other languages), but of course, it isn't standard. It's also only available in newer versions of Objective-C Section 16.10: Getting a Value from NSDictionary There are multiple ways to get an object from an NSDictionary with a key. For instance, to get a lamborghini from a list of cars Standard Car * lamborghini = [cars objectForKey:@"Lamborghini"]; Just like any other object, call the method of NSDictionary that gives you an object for a key, objectForKey:. Be careful not to confuse this with valueForKey:; that's for a completely different thing, Key Value Coding Shorthand Car * lamborghini = cars[@"Lamborghini"]; This is the syntax that you use for dictionaries in most other languages, such as C#, Java, and JavaScript. It's much more convenient than the standard syntax, and arguably more readable (especially if you code in these other languages), but of course, it isn't standard. It's also only available in newer versions of Objective-C Section 16.11: Check if NSDictionary already has a key or not Objective-C: //this is the dictionary you start with. NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:@"name1", @"Sam",@"name2", @"Sanju",nil]; //check if the dictionary contains the key you are going to modify. In this example, @"Sam" if (dict[@"name1"] != nil) { //there is an entry for Key name1 } else { //There is no entry for name1 } Section 16.12: Block Based Enumeration Enumerating dictionaries allows you to run a block of code on each dictionary key-value pair using the method enumerateKeysAndObjectsUsingBlock:(void (^)(id key, id obj, BOOL *stop))block Example: NSDictionary stockSymbolsDictionary = @{ GoalKicker.com – Objective-C® Notes for Professionals 50 @"AAPL": @"Apple", @"GOOGL": @"Alphabet", @"MSFT": @"Microsoft", @"AMZN": @"Amazon" }; NSLog(@"Printing contents of dictionary via enumeration"); [stockSymbolsDictionary enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) { NSLog(@"Key: %@, Value: %@", key, obj); }]; GoalKicker.com – Objective-C® Notes for Professionals 51 Chapter 17: NSMutableDictionary objects keys An array containing the values for the new dictionary. CellAn array containing the keys for the new dictionary. Each key is copied and the copy is added to the dictionary. Section 17.1: NSMutableDictionary Example + dictionaryWithCapacity: Creates and returns a mutable dictionary, initially giving it enough allocated memory to hold a given number of entries. NSMutableDictionary *dict = [NSMutableDictionary dictionaryWithCapacity:1]; NSLog(@"%@",dict); - init Initializes a newly allocated mutable dictionary. NSMutableDictionary *dict = [[NSMutableDictionary alloc] init]; NSLog(@"%@",dict); + dictionaryWithSharedKeySet: Creates a mutable dictionary which is optimized for dealing with a known set of keys. id sharedKeySet = [NSDictionary sharedKeySetForKeys:@[@"key1", @"key2"]]; // returns NSSharedKeySet NSMutableDictionary *dict = [NSMutableDictionary dictionaryWithSharedKeySet:sharedKeySet]; dict[@"key1"] = @"Easy"; dict[@"key2"] = @"Tutorials"; //We can an object that is not in the shared keyset dict[@"key3"] = @"Website"; NSLog(@"%@",dict); Output { key1 = Easy; key2 = Tutorials; key3 = Website; } Adding Entries to a Mutable Dictionary - setObject:forKey: Adds a given key-value pair to the dictionary. NSMutableDictionary *dict = [NSMutableDictionary dictionary]; [dict setObject:@"Easy" forKey:@"Key1"]; NSLog(@"%@",dict); GoalKicker.com – Objective-C® Notes for Professionals 52 Output { Key1 = Eezy; } - setObject:forKeyedSubscript: Adds a given key-value pair to the dictionary. NSMutableDictionary *dict = [NSMutableDictionary dictionary]; [dict setObject:@"Easy" forKeyedSubscript:@"Key1"]; NSLog(@"%@",dict); Output { Key1 = Easy; } Section 17.2: Removing Entries From a Mutable Dictionary - removeObjectForKey: Removes a given key and its associated value from the dictionary. NSMutableDictionary *dict = [NSMutableDictionary dictionaryWithDictionary:@{@"key1":@"Easy",@"key2": @"Tutorials"}]; [dict removeObjectForKey:@"key1"]; NSLog(@"%@",dict); OUTPUT { key2 = Tutorials; } - removeAllObjects Empties the dictionary of its entries. NSMutableDictionary *dict = [NSMutableDictionary dictionaryWithDictionary:@{@"key1":@"Eezy",@"key2": @"Tutorials"}]; [dict removeAllObjects]; NSLog(@"%@",dict); OUTPUT GoalKicker.com – Objective-C® Notes for Professionals 53 { } - removeObjectsForKeys: Removes from the dictionary entries specified by elements in a given array. NSMutableDictionary *dict = [NSMutableDictionary dictionaryWithDictionary:@{@"key1":@"Easy",@"key2": @"Tutorials"}]; [dict removeObjectsForKeys:@[@"key1"]]; NSLog(@"%@",dict); OUTPUT { key2 = Tutorials; } GoalKicker.com – Objective-C® Notes for Professionals 54 Chapter 18: NSDate Section 18.1: Convert NSDate that is composed from hour and minute (only) to a full NSDate There are many cases when one has created an NSDate from only an hour and minute format, i.e: 08:12 The downside for this situation is that your NSDate is almost completely "naked" and what you need to do is to create: day, month, year, second and time zone in order to this object to "play along" with other NSDate types. For the sake of the example let's say that hourAndMinute is the NSDate type that is composed from hour and minute format: NSDateComponents *hourAndMintuteComponents = [calendar components:NSCalendarUnitHour | NSCalendarUnitMinute fromDate:hourAndMinute]; NSDateComponents *componentsOfDate = [[NSCalendar currentCalendar] components:NSCalendarUnitDay | NSCalendarUnitMonth | NSCalendarUnitYear fromDate:[NSDate date]]; NSDateComponents *components = [[NSDateComponents alloc] init]; [components setDay: componentsOfDate.day]; [components setMonth: componentsOfDate.month]; [components setYear: componentsOfDate.year]; [components setHour: [hourAndMintuteComponents hour]]; [components setMinute: [hourAndMintuteComponents minute]]; [components setSecond: 0]; [calendar setTimeZone: [NSTimeZone defaultTimeZone]]; NSDate *yourFullNSDateObject = [calendar dateFromComponents:components]; Now your object is the total opposite of being "naked". Section 18.2: Converting NSDate to NSString If ww have NSDate object, and we want to convert it into NSString. There are different types of Date strings. How we can do that?, It is very simple. Just 3 steps. 1. Create NSDateFormatter Object NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init]; 2. Set the date format in which you want your string. dateFormatter.dateFormat = @"yyyy-MM-dd 'at' HH:mm"; 3. Now, get the formatted string NSDate *date = [NSDate date]; // your NSDate object NSString *dateString = [dateFormatter stringFromDate:date]; This will give output something like this: 2001-01-02 at 13:00 Note: GoalKicker.com – Objective-C® Notes for Professionals 55 Creating an NSDateFormatter instance is an expensive operation, so it is recommended to create it once and reuse when possible. Section 18.3: Creating an NSDate The NSDate class provides methods for creating NSDate objects corresponding to a given date and time. An NSDate can be initialized using the designated initializer, which: Returns an NSDate object initialized relative to 00:00:00 UTC on 1 January 2001 by a given number of seconds. NSDate *date = [[NSDate alloc] initWithTimeIntervalSinceReferenceDate:100.0]; NSDate also provides an easy way to create an NSDate equal to the current date and time: NSDate *now = [NSDate date]; It is also possible to create an NSDate a given amount of seconds from the current date and time: NSDate *tenSecondsFromNow = [NSDate dateWithTimeIntervalSinceNow:10.0]; Section 18.4: Date Comparison There are 4 methods for comparing NSDates in Objective-C: - (BOOL)isEqualToDate:(NSDate *)anotherDate - (NSDate *)earlierDate:(NSDate *)anotherDate - (NSDate *)laterDate:(NSDate *)anotherDate - (NSComparisonResult)compare:(NSDate *)anotherDate Consider the following example using 2 dates, NSDate date1 = July 7, 2016 and NSDate date2 = July 2, 2016: NSDateComponents *comps1 = [[NSDateComponents alloc]init]; comps.year = 2016; comps.month = 7; comps.day = 7; NSDateComponents *comps2 = [[NSDateComponents alloc]init]; comps.year = 2016; comps.month = 7; comps.day = 2; NSDate* date1 = [calendar dateFromComponents:comps1]; //Initialized as July 7, 2016 NSDate* date2 = [calendar dateFromComponents:comps2]; //Initialized as July 2, 2016 Now that the NSDates are created, they can be compared: if ([date1 isEqualToDate:date2]) { //Here it returns false, as both dates are not equal } We can also use the earlierDate: and laterDate: methods of the NSDate class: NSDate *earlierDate = [date1 earlierDate:date2];//Returns the earlier of 2 dates. Here earlierDate GoalKicker.com – Objective-C® Notes for Professionals 56 will equal date2. NSDate *laterDate = [date1 laterDate:date2];//Returns the later of 2 dates. Here laterDate will equal date1. Lastly, we can use NSDate's compare: method: NSComparisonResult result = [date1 compare:date2]; if (result == NSOrderedAscending) { //Fails //Comes here if date1 is earlier than date2. In our case it will not come here. }else if (result == NSOrderedSame){ //Fails //Comes here if date1 is the same as date2. In our case it will not come here. }else{//NSOrderedDescending //Succeeds //Comes here if date1 is later than date2. In our case it will come here } GoalKicker.com – Objective-C® Notes for Professionals 57 Chapter 19: NSURL Section 19.1: Create From NSString: NSString *urlString = @"https://www.stackoverflow.com"; NSURL *myUrl = [NSURL URLWithString: urlString]; You can also use the following methods: - initWithString: + URLWithString:relativeToURL: - initWithString:relativeToURL: + fileURLWithPath:isDirectory: - initFileURLWithPath:isDirectory: + fileURLWithPath: - initFileURLWithPath: Designated Initializer + fileURLWithPathComponents: + URLByResolvingAliasFileAtURL:options:error: + URLByResolvingBookmarkData:options:relativeToURL:bookmarkDataIsStale:error: - initByResolvingBookmarkData:options:relativeToURL:bookmarkDataIsStale:error: + fileURLWithFileSystemRepresentation:isDirectory:relativeToURL: - getFileSystemRepresentation:maxLength: - initFileURLWithFileSystemRepresentation:isDirectory:relativeToURL: Section 19.2: Compare NSURL NSString *urlString = @"https://www.stackoverflow.com"; NSURL *myUrl = [NSURL URLWithString: urlString]; NSURL *myUrl2 = [NSURL URLWithString: urlString]; if ([myUrl isEqual:myUrl2]) return YES; Section 19.3: Modifying and Converting a File URL with removing and appending path 1. URLByDeletingPathExtension: If the receiver represents the root path, this property contains a copy of the original URL. If the URL has multiple path extensions, only the last one is removed. 2. URLByAppendingPathExtension: Returns a new URL made by appending a path extension to the original URL. Example: NSUInteger count = 0; NSString *filePath = nil; do { NSString *extension = ( NSString *)UTTypeCopyPreferredTagWithClass(( CFStringRef)AVFileTypeQuickTimeMovie, kUTTagClassFilenameExtension); NSString *fileNameNoExtension = [[asset.defaultRepresentation.url GoalKicker.com – Objective-C® Notes for Professionals 58 URLByDeletingPathExtension] lastPathComponent];//Delete is used NSString *fileName = [NSString stringWithFormat:@"%@-%@-%u",fileNameNoExtension , AVAssetExportPresetLowQuality, count]; filePath = NSTemporaryDirectory(); filePath = [filePath stringByAppendingPathComponent:fileName];//Appending is used filePath = [filePath stringByAppendingPathExtension:extension]; count++; } while ([[NSFileManager defaultManager] fileExistsAtPath:filePath]); NSURL *outputURL = [NSURL fileURLWithPath:filePath]; GoalKicker.com – Objective-C® Notes for Professionals 59 Chapter 20: NSUrl send a post request Section 20.1: Simple POST request // Create the request. NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"http://google.com"]]; // Specify that it will be a POST request request.HTTPMethod = @"POST"; // This is how we set header fields [request setValue:@"application/xml; charset=utf-8" forHTTPHeaderField:@"Content-Type"]; // Convert your data and set your request's HTTPBody property NSString *stringData = @"some data"; NSData *requestBodyData = [stringData dataUsingEncoding:NSUTF8StringEncoding]; request.HTTPBody = requestBodyData; // Create url connection and fire request NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:request delegate:self]; Section 20.2: Simple Post Request With Timeout // Create the request. NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:@"http://google.com"]]; // Specify that it will be a POST request request.HTTPMethod = @"POST"; // Setting a timeout request.timeoutInterval = 20.0; // This is how we set header fields [request setValue:@"application/xml; charset=utf-8" forHTTPHeaderField:@"Content-Type"]; // Convert your data and set your request's HTTPBody property NSString *stringData = @"some data"; NSData *requestBodyData = [stringData dataUsingEncoding:NSUTF8StringEncoding]; request.HTTPBody = requestBodyData; // Create url connection and fire request NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:request delegate:self]; GoalKicker.com – Objective-C® Notes for Professionals 60 Chapter 21: NSData Section 21.1: Create From NSString: NSString *str = @"Hello world"; NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding]; From Int: int i = 1; NSData *data = [NSData dataWithBytes: &i length: sizeof(i)]; You can also use the following methods: + dataWithContentsOfURL: + dataWithContentsOfURL:options:error: + dataWithData: - initWithBase64EncodedData:options: - initWithBase64EncodedString:options: - initWithBase64Encoding: - initWithBytesNoCopy:length: - initWithBytesNoCopy:length:deallocator: - initWithBytesNoCopy:length:freeWhenDone: - initWithContentsOfFile: - initWithContentsOfFile:options:error: - initWithContentsOfMappedFile: - initWithContentsOfURL: - initWithContentsOfURL:options:error: - initWithData: Section 21.2: NSData and Hexadecimal String Get NSData from Hexadecimal String + (NSData *)dataFromHexString:(NSString *)string { string = [string lowercaseString]; NSMutableData *data= [NSMutableData new]; unsigned char whole_byte; char byte_chars[3] = {'\0','\0','\0'}; int i = 0; int length = (int) string.length; while (i < length-1) { char c = [string characterAtIndex:i++]; if (c < '0' || (c > '9' && c < 'a') || c > 'f') continue; byte_chars[0] = c; byte_chars[1] = [string characterAtIndex:i++]; whole_byte = strtol(byte_chars, NULL, 16); [data appendBytes:&whole_byte length:1]; } return data; } Get Hexadecimal String from data: GoalKicker.com – Objective-C® Notes for Professionals 61 + (NSString *)hexStringForData:(NSData *)data { if (data == nil) { return nil; } NSMutableString *hexString = [NSMutableString string]; const unsigned char *p = [data bytes]; for (int i=0; i < [data length]; i++) { [hexString appendFormat:@"%02x", *p++]; } return hexString; } Section 21.3: Get NSData length NSString *filePath = [[NSFileManager defaultManager] pathForRessorce: @"data" ofType:@"txt"]; NSData *data = [NSData dataWithContentsOfFile:filePath]; int len = [data length]; Section 21.4: Encoding and decoding a string using NSData Base64 Encoding //Create a Base64 Encoded NSString Object NSData *nsdata = [@"iOS Developer Tips encoded in Base64" dataUsingEncoding:NSUTF8StringEncoding]; // Get NSString from NSData object in Base64 NSString *base64Encoded = [nsdata base64EncodedStringWithOptions:0]; // Print the Base64 encoded string NSLog(@"Encoded: %@", base64Encoded); Decoding: // NSData from the Base64 encoded str NSData *nsdataFromBase64String = [[NSData alloc]initWithBase64EncodedString:base64Encoded options:0]; // Decoded NSString from the NSData NSString *base64Decoded = [[NSString alloc] initWithData:nsdataFromBase64String encoding:NSUTF8StringEncoding]; NSLog(@"Decoded: %@", base64Decoded); GoalKicker.com – Objective-C® Notes for Professionals 62 Chapter 22: NSPredicate Section 22.1: Filter By Name NSArray *array = @[ @{ @"id": @"7CDF6D22-8D36-49C2-84FE-E31EECCECB71", @"title": @"Jackie Chan Strike Movie", @"url": @"http://abc.com/playback.m3u8", @"thumbnailURL": @"http://abc.com/thumbnail.png", @"isMovie" : @1 }, @{ @"id": @"7CDF6D22-8D36-49C2-84FE-E31EECCECB72", @"title": @"Sherlock homes", @"url": @"http://abc.com/playback.m3u8", @"thumbnailURL": @"http://abc.com/thumbnail.png", @"isMovie" : @0 }, @{ @"id": @"7CDF6D22-8D36-49C2-84FE-E31EECCECB73", @"title": @"Titanic", @"url": @"http://abc.com/playback.m3u8", @"thumbnailURL": @"http://abc.com/thumbnail.png", @"isMovie" : @1 }, @{ @"id": @"7CDF6D22-8D36-49C2-84FE-E31EECCECB74", @"title": @"Star Wars", @"url": @"http://abc.com/playback.m3u8", @"thumbnailURL": @"http://abc.com/thumbnail.png", @"isMovie" : @1 }, @{ @"id": @"7CDF6D22-8D36-49C2-84FE-E31EECCECB75", @"title": @"Pokemon", @"url": @"http://abc.com/playback.m3u8", @"thumbnailURL": @"http://abc.com/thumbnail.png", @"isMovie" : @0 }, @{ @"id": @"7CDF6D22-8D36-49C2-84FE-E31EECCECB76", @"title": @"Avatar", @"url": @"http://abc.com/playback.m3u8", @"thumbnailURL": @"http://abc.com/thumbnail.png", @"isMovie" : @1 }, @{ @"id": @"7CDF6D22-8D36-49C2-84FE-E31EECCECB77", @"title": @"Popey", @"url": @"http://abc.com/playback.m3u8", @"thumbnailURL": @"http://abc.com/thumbnail.png", @"isMovie" : @1 }, @{ @"id": @"7CDF6D22-8D36-49C2-84FE-E31EECCECB78", @"title": @"Tom and Jerry", @"url": @"http://abc.com/playback.m3u8", @"thumbnailURL": @"http://abc.com/thumbnail.png", @"isMovie" : @1 GoalKicker.com – Objective-C® Notes for Professionals 63 }, @{ @"id": @"7CDF6D22-8D36-49C2-84FE-E31EECCECB79", @"title": @"The wolf", @"url": @"http://abc.com/playback.m3u8", @"thumbnailURL": @"http://abc.com/thumbnail.png", @"isMovie" : @1 } ]; // *** Case Insensitive comparison with exact title match *** NSPredicate *filterByNameCIS = [NSPredicate predicateWithFormat:@"self.title LIKE[cd] %@",@"Tom and Jerry"]; NSLog(@"Filter By Name(CIS) : %@",[array filteredArrayUsingPredicate:filterByNameCIS]); Section 22.2: Find movies except given ids // *** Find movies except given ids *** NSPredicate *filterByNotInIds = [NSPredicate predicateWithFormat:@"NOT (self.id IN %@)",@[@"7CDF6D22-8D36-49C2-84FE-E31EECCECB79", @"7CDF6D22-8D36-49C2-84FE-E31EECCECB76"]]; NSLog(@"Filter movies except given Ids : %@",[array filteredArrayUsingPredicate:filterByNotInIds]); Section 22.3: Find all the objects which is of type movie // *** Find all the objects which is of type movie, Both the syntax are valid *** NSPredicate *filterByMovieType = [NSPredicate predicateWithFormat:@"self.isMovie = %@",@1]; // OR //NSPredicate *filterByMovieType = [NSPredicate predicateWithFormat:@"self.isMovie = %@",[NSNumber numberWithBool:YES]]; NSLog(@"Filter By Movie Type : %@",[array filteredArrayUsingPredicate:filterByMovieType]); Section 22.4: Find Distinct object ids of array // *** Find Distinct object ids of array *** NSLog(@"Distinct id : %@",[array valueForKeyPath:@"@distinctUnionOfObjects.id"]); Section 22.5: Find movies with specific ids // *** Find movies with specific ids *** NSPredicate *filterByIds = [NSPredicate predicateWithFormat:@"self.id IN %@",@[@"7CDF6D22-8D36-49C2-84FE-E31EECCECB79", @"7CDF6D22-8D36-49C2-84FE-E31EECCECB76"]]; NSLog(@"Filter By Ids : %@",[array filteredArrayUsingPredicate:filterByIds]); Section 22.6: Case Insensitive comparison with exact title match // *** Case Insensitive comparison with exact title match *** NSPredicate *filterByNameCIS = [NSPredicate predicateWithFormat:@"self.title LIKE[cd] %@",@"Tom and Jerry"]; NSLog(@"Filter By Name(CIS) : %@",[array filteredArrayUsingPredicate:filterByNameCIS]); Section 22.7: Case sensitive with exact title match // *** Case sensitive with exact title match *** NSPredicate *filterByNameCS = [NSPredicate predicateWithFormat:@"self.title = %@",@"Tom and GoalKicker.com – Objective-C® Notes for Professionals 64 Jerry"]; NSLog(@"Filter By Name(CS) : %@",[array filteredArrayUsingPredicate:filterByNameCS]); Section 22.8: Case Insensitive comparison with matching subset // *** Case Insensitive comparison with matching subset *** NSPredicate *filterByName = [NSPredicate predicateWithFormat:@"self.title CONTAINS[cd] %@",@"Tom"]; NSLog(@"Filter By Containing Name : %@",[array filteredArrayUsingPredicate:filterByName]); GoalKicker.com – Objective-C® Notes for Professionals 65 Chapter 23: NSRegularExpression Section 23.1: Check whether a string matches a pattern NSString *testString1 = @"(555) 123-5678"; NSString *testString2 = @"not a phone number"; NSError *error = nil; NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"^\\(\\d{3}\\) \\d{3}\\-\\d{4}$" options:NSRegularExpressionCaseInsensitive error:&error]; NSInteger result1 = [regex numberOfMatchesInString:testString1 options:0 range:NSMakeRange(0, testString1.length)]; NSInteger result2 = [regex numberOfMatchesInString:testString2 options:0 range:NSMakeRange(0, testString2.length)]; NSLog(@"Is string 1 a phone number? %@", result1 > 0 ? @"YES" : @"NO"); NSLog(@"Is string 2 a phone number? %@", result2 > 0 ? @"YES" : @"NO"); The output will show that the first string is a phone number and the second one isn't. Section 23.2: Find all the numbers in a string NSString *testString = @"There are 42 sheep and 8672 cows."; NSError *error = nil; NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(\\d+)" options:NSRegularExpressionCaseInsensitive error:&error]; NSArray *matches = [regex matchesInString:testString options:0 range:NSMakeRange(0, testString.length)]; for (NSTextCheckingResult *matchResult in matches) { NSString* match = [testString substringWithRange:matchResult.range]; NSLog(@"match: %@", match); } The output will be match: 42 and match: 8672. GoalKicker.com – Objective-C® Notes for Professionals 66 Chapter 24: NSJSONSerialization Operator Description data A data object containing JSON data opt Options for reading the JSON data and creating the Foundation objects. error If an error occurs, upon return contains an NSError object that describes the problem. Section 24.1: JSON Parsing using NSJSONSerialization Objective-C NSError *e = nil; NSString *jsonString = @"[{\"id\": \"1\", \"name\":\"sam\"}]"; NSData *data = [jsonString dataUsingEncoding:NSUTF8StringEncoding]; NSArray *jsonArray = [NSJSONSerialization JSONObjectWithData: data options: NSJSONReadingMutableContainers error: &e]; if (!jsonArray) { NSLog(@"Error parsing JSON: %@", e); } else { for(NSDictionary *item in jsonArray) { NSLog(@"Item: %@", item); } } Output: Item: { id = 1; name = sam; } Example 2: Using contents of url: //Parsing: NSData *data = [NSData dataWithContentsOfURL:@“URL HERE”]; NSError *error; NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error]; NSLog(@“json :%@”,json); Sample response: json: { MESSAGE = "Test Message"; RESPONSE =( { email = "[email protected]"; id = 15; phone = 1234567890; name = Staffy; } ); STATUS = SUCCESS; GoalKicker.com – Objective-C® Notes for Professionals 67 } NSMutableDictionary *response = [[[json valueForKey:@"RESPONSE"] objectAtIndex:0]mutableCopy]; NSString *nameStr = [response valueForKey:@"name"]; NSString *emailIdStr = [response valueForKey:@"email"]; GoalKicker.com – Objective-C® Notes for Professionals 68 Chapter 25: NSCalendar Section 25.1: System Locale Information +currentCalendar returns the logical calendar for the current user. NSCalendar *calendar = [NSCalendar currentCalendar]; NSLog(@"%@",calendar); +autoupdatingCurrentCalendar returns the current logical calendar for the current user. NSCalendar *calendar = [NSCalendar autoupdatingCurrentCalendar]; NSLog(@"%@",calendar); Section 25.2: Initializing a Calendar - initWithCalendarIdentifier: Initializes a newly-allocated NSCalendar object for the calendar specified by a given identifier. NSCalendar *calender = [[NSCalendar alloc]initWithCalendarIdentifier:@"gregorian"]; NSLog(@"%@",calender); - setFirstWeekday: Sets the index of the first weekday for the receiver. NSCalendar *calender = [NSCalendar autoupdatingCurrentCalendar]; [calender setFirstWeekday:1]; NSLog(@"%d",[calender firstWeekday]); - setLocale: Sets the locale for the receiver. NSCalendar *calender = [NSCalendar autoupdatingCurrentCalendar]; [calender setLocale:[NSLocale currentLocale]]; NSLog(@"%@",[calender locale]); - setMinimumDaysInFirstWeek: Sets the minimum number of days in the first week of the receiver. NSCalendar *calender = [NSCalendar autoupdatingCurrentCalendar]; [calender setMinimumDaysInFirstWeek:7]; NSLog(@"%d",[calender minimumDaysInFirstWeek]); - setTimeZone: Sets the time zone for the receiver. NSCalendar *calender = [NSCalendar autoupdatingCurrentCalendar]; [calender setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]]; NSLog(@"%@",[calender timeZone]); Section 25.3: Calendrical Calculations - components:fromDate: Returns a NSDateComponents object containing a given date decomposed into specified components NSCalendar *calender = [NSCalendar autoupdatingCurrentCalendar]; [calender setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]]; NSLog(@"%@",[calender components:NSCalendarUnitDay fromDate:[NSDate date]]); GoalKicker.com – Objective-C® Notes for Professionals 69 NSLog(@"%@",[calender components:NSCalendarUnitYear fromDate:[NSDate date]]); NSLog(@"%@",[calender components:NSCalendarUnitMonth fromDate:[NSDate date]]); - components:fromDate:toDate:options: Returns, as an NSDateComponents object using specified components, the difference between two supplied dates. NSCalendar *calender = [NSCalendar autoupdatingCurrentCalendar]; [calender setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]]; NSLog(@"%@",[calender components:NSCalendarUnitYear fromDate:[NSDate dateWithTimeIntervalSince1970:0] toDate:[NSDate dateWithTimeIntervalSinceNow:18000] options:NSCalendarWrapComponents]); - dateByAddingComponents:toDate:options: Returns a new NSDate object representing the absolute time calculated by adding given components to a given date. NSCalendar *calender = [NSCalendar autoupdatingCurrentCalendar]; NSDateComponents *dateComponent = [[NSDateComponents alloc]init]; [dateComponent setYear:10]; NSLog(@"%@",[calender dateByAddingComponents:dateComponent toDate:[NSDate dateWithTimeIntervalSinceNow:0] options:NSCalendarWrapComponents] ); - dateFromComponents: Returns a new NSDate object representing the absolute time calculated from given components. NSCalendar *calender = [NSCalendar autoupdatingCurrentCalendar]; NSDateComponents *dateComponent = [[NSDateComponents alloc]init]; [dateComponent setYear:2020]; NSLog(@"%@",[calender dateFromComponents:dateComponent]); GoalKicker.com – Objective-C® Notes for Professionals 70 Chapter 26: NSAttributedString Section 26.1: Using Enumerating over Attributes in a String and underline part of string NSMutableDictionary *attributesDictionary = [NSMutableDictionary dictionary]; [attributesDictionary setObject:[UIFont systemFontOfSize:14] forKey:NSFontAttributeName]; //[attributesDictionary setObject:[UIColor redColor] forKey:NSForegroundColorAttributeName]; NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc]initWithString:@"Google www.google.com link" attributes:attributesDictionary]; [attributedString enumerateAttribute:(NSString *) NSFontAttributeName inRange:NSMakeRange(0, [attributedString length]) options:NSAttributedStringEnumerationLongestEffectiveRangeNotRequired usingBlock:^(id value, NSRange range, BOOL *stop) { NSLog(@"Attribute: %@, %@", value, NSStringFromRange(range)); }]; NSMutableAttributedString *attributedStr = [[NSMutableAttributedString alloc] initWithString:@"www.google.com "]; [attributedString addAttribute:NSUnderlineStyleAttributeName value:[NSNumber numberWithInt:NSUnderlineStyleDouble] range:NSMakeRange(7, attributedStr.length)]; [attributedString addAttribute:NSForegroundColorAttributeName value:[UIColor blueColor] range:NSMakeRange(6,attributedStr.length)]; _attriLbl.attributedText = attributedString;//_attriLbl (of type UILabel) added in storyboard Output: Section 26.2: Creating a string that has custom kerning (letter spacing) editshare NSAttributedString (and its mutable sibling NSMutableAttributedString) allows you to create strings that are complex in their appearance to the user. A common application is to use this to display a string and adding custom kerning / letter-spacing. This would be achieved as follows (where label is a UILabel), giving a different kerning for the word "kerning" NSMutableAttributedString *attributedString; attributedString = [[NSMutableAttributedString alloc] initWithString:@"Apply kerning"]; [attributedString addAttribute:NSKernAttributeName value:@5 range:NSMakeRange(6, 7)]; [label setAttributedText:attributedString]; Section 26.3: Create a string with text struck through NSMutableAttributedString *attributeString = [[NSMutableAttributedString alloc] initWithString:@"Your String here"]; [attributeString addAttribute:NSStrikethroughStyleAttributeName GoalKicker.com – Objective-C® Notes for Professionals 71 value:@2 range:NSMakeRange(0, [attributeString length])]; Section 26.4: How you create a tri-color attributed string NSMutableAttributedString * string = [[NSMutableAttributedString alloc] initWithString:@"firstsecondthird"]; [string addAttribute:NSForegroundColorAttributeName value:[UIColor redColor] range:NSMakeRange(0,5)]; [string addAttribute:NSForegroundColorAttributeName value:[UIColor greenColor] range:NSMakeRange(5,6)]; [string addAttribute:NSForegroundColorAttributeName value:[UIColor blueColor] range:NSMakeRange(11,5)]; Range : start to end string Here we have firstsecondthird string so in first we have set range (0,5) so from starting first character to fifth character it will display in green text color. GoalKicker.com – Objective-C® Notes for Professionals 72 Chapter 27: NSTimer Section 27.1: Storing information in the Timer When creating a timer, you can set the userInfo parameter to include information that you want to pass to the function you call with the timer. By taking a timer as a parameter in said function, you can access the userInfo property. NSDictionary *dictionary = @{ @"Message" : @"Hello, world!" }; //this dictionary contains a message [NSTimer scheduledTimerWithTimeInterval:5.0 target:self selector:@selector(doSomething) userInfo:dictionary repeats:NO]; //the timer contains the dictionary and later calls the function ... - (void) doSomething:(NSTimer*)timer{ //the function retrieves the message from the timer NSLog("%@", timer.userInfo["Message"]); } Section 27.2: Creating a Timer This will create a timer to call the doSomething method on self in 5.0 seconds. [NSTimer scheduledTimerWithTimeInterval:5.0 target:self selector:@selector(doSomething) userInfo:nil repeats:NO]; Setting the repeats parameter to false/NO indicates that we want the timer to fire only once. If we set this to true/YES, it would fire every five seconds until manually invalidated. Section 27.3: Invalidating a timer [timer invalidate]; timer = nil; This will stop the timer from firing. Must be called from the thread the timer was created in, see Apple's notes: You must send this message from the thread on which the timer was installed. If you send this message from another thread, the input source associated with the timer may not be removed from its run loop, which could prevent the thread from exiting properly. Setting nil will help you next to check whether it's running or not. if(timer) { [timer invalidate]; timer = nil; GoalKicker.com – Objective-C® Notes for Professionals 73