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Diffstat (limited to 'objective-c.html.markdown')
| -rw-r--r-- | objective-c.html.markdown | 114 |
1 files changed, 64 insertions, 50 deletions
diff --git a/objective-c.html.markdown b/objective-c.html.markdown index 406b2e92..a70351b5 100644 --- a/objective-c.html.markdown +++ b/objective-c.html.markdown @@ -4,6 +4,7 @@ language: Objective-C contributors: - ["Eugene Yagrushkin", "www.about.me/yagrushkin"] - ["Yannick Loriot", "https://github.com/YannickL"] + - ["Levi Bostian", "https://github.com/levibostian"] filename: LearnObjectiveC.m --- @@ -28,7 +29,9 @@ int main (int argc, const char * argv[]) { // Create an autorelease pool to manage the memory into the program NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; - + // If using automatic reference counting (ARC), use @autoreleasepool instead: + @autoreleasepool { + // Use NSLog to print lines to the console NSLog(@"Hello World!"); // Print the string "Hello World!" @@ -74,16 +77,16 @@ int main (int argc, const char * argv[]) short fortyTwoShort = [fortyTwoShortNumber shortValue]; // or 42 NSLog(@"%hi", fortyTwoShort); - NSNumber *fortyTwoShortNumber = [NSNumber numberWithShort:41]; - unsigned short fortyTwoUnsigned = [fortyTwoShortNumber unsignedShortValue]; // or 41 - NSLog(@"%hu", fortyTwoUnsigned); + NSNumber *fortyOneShortNumber = [NSNumber numberWithShort:41]; + unsigned short fortyOneUnsigned = [fortyOneShortNumber unsignedShortValue]; // or 41 + NSLog(@"%u", fortyOneUnsigned); NSNumber *fortyTwoLongNumber = @42L; long fortyTwoLong = [fortyTwoLongNumber longValue]; // or 42 NSLog(@"%li", fortyTwoLong); - NSNumber *fortyTwoLongNumber = @53L; - unsigned long fiftyThreeUnsigned = [fortyTwoLongNumber unsignedLongValue]; // or 53 + NSNumber *fiftyThreeLongNumber = @53L; + unsigned long fiftyThreeUnsigned = [fiftyThreeLongNumber unsignedLongValue]; // or 53 NSLog(@"%lu", fiftyThreeUnsigned); // Floating point literals @@ -116,6 +119,7 @@ int main (int argc, const char * argv[]) NSLog(@"%i", yesBool); // prints => 1 // Array object + // May contain different data types, but must be an Objective-C object. NSArray *anArray = @[@1, @2, @3, @4]; NSNumber *thirdNumber = anArray[2]; NSLog(@"Third number = %@", thirdNumber); // Print "Third number = 3" @@ -146,10 +150,6 @@ int main (int argc, const char * argv[]) [mutableSet addObject:@"Hello"]; NSLog(@"%@", mutableSet); // prints => {(Hello)} - // Set object - NSSet *set = [NSSet setWithObjects:@"Hello", @"Hello", @"World", nil]; - NSLog(@"%@", set); // prints => {(Hello, World)} - /////////////////////////////////////// // Operators /////////////////////////////////////// @@ -267,6 +267,9 @@ int main (int argc, const char * argv[]) // Clean up the memory you used into your program [pool drain]; + + // End of @autoreleasepool. + } // End the program return 0; @@ -276,41 +279,30 @@ int main (int argc, const char * argv[]) // Classes And Functions /////////////////////////////////////// -// Declare your class in a header(MyClass.h) file: -// Class Declaration Syntax: +// Declare your class in a header file (MyClass.h): +// Class declaration syntax: // @interface ClassName : ParentClassName <ImplementedProtocols> // { -// Member variable declarations; +// type name; <= variable declarations; // } -// -/+ (type) Method declarations; +// @property type name; <= property declarations. +// -/+ (type) Method declarations; <= Method declarations. // @end -@interface MyClass : NSObject <MyProtocol> +@interface MyClass : NSObject <MyProtocol> // NSObject is Objective-C's base object class. { - // Instance variable declarations (can exist in either interface or implementation file) + // Instance variable declarations (can exist in either interface or implementation file). int count; // Protected access by default. - @private id data; // Private access. (More convenient to declare in implementation file) + @private id data; // Private access. (More convenient to declare in implementation file). NSString *name; } -// Convenient notation to auto generate public access getter and setter -@property int count; -@property (copy) NSString *name; // Copy the object during assignment. -@property (readonly) id data; // Declare only a getter method. -// To access public variable in implementation file, use '_' followed by variable name: -_count = 5; -NSLog(@"%d", _count); // prints => 5 -// To access public variable outside implementation file, @property generates setter method -// automatically. Method name is 'set' followed by @property variable name: -MyClass *myClass = [[MyClass alloc] init]; // create MyClass object instance. -[myClass setCount:10]; -NSLog(@"%@", [myClass count]); // prints => 10 +// Convenient notation for public access variables to auto generate a setter method. +// By default, setter method name is 'set' followed by @property variable name. +@property int count; // Setter method name = 'setCount' +@property (copy) NSString *name; // (copy) => Copy the object during assignment. +@property (readonly) id data; // (readonly) => Cannot set value outside interface. // You can customize the getter and setter names instead of using default 'set' name: -@property (getter=countGet, setter=countSet:) int count; -[myClass countSet:32]; -NSLog(@"%i", [myClass countGet]); // prints => 32 -// For convenience, you may use dot notation to set object instance variables: -myClass.count = 45; -NSLog(@"%i", myClass.count); // prints => 45 - +@property (getter=lengthGet, setter=lengthSet:) int length; + // Methods +/- (return type)methodSignature:(Parameter Type *)parameterName; @@ -321,20 +313,39 @@ NSLog(@"%i", myClass.count); // prints => 45 - (NSString *)instanceMethodWithParameter:(NSString *)string; - (NSNumber *)methodAParameterAsString:(NSString*)string andAParameterAsNumber:(NSNumber *)number; -@end +@end // States the end of the interface. + + +// To access public variables from the implementation file, @property generates a setter method +// automatically. Method name is 'set' followed by @property variable name: +MyClass *myClass = [[MyClass alloc] init]; // create MyClass object instance. +[myClass setCount:10]; +NSLog(@"%d", [myClass count]); // prints => 10 +// Or using the custom getter and setter method defined in @interface: +[myClass lengthSet:32]; +NSLog(@"%i", [myClass lengthGet]); // prints => 32 +// For convenience, you may use dot notation to set and access object instance variables: +myClass.count = 45; +NSLog(@"%i", myClass.count); // prints => 45 + // Implement the methods in an implementation (MyClass.m) file: @implementation MyClass { - long count; // Private access instance variable. + long distance; // Private access instance variable. } +// To access a public variable from the interface file, use '_' followed by variable name: +_count = 5; // References "int count" from MyClass interface. +// Access variables defined in implementation file: +distance = 18; // References "long distance" from MyClass implementation. + // Call when the object is releasing - (void)dealloc { } // Constructors are a way of creating classes -// This is a default constructor which is called when the object is creating +// This is a default constructor which is called when the object is initialized. - (id)init { if ((self = [super init])) @@ -365,7 +376,7 @@ NSLog(@"%i", myClass.count); // prints => 45 // statements } -@end +@end // States the end of the implementation. /* * A protocol declares methods that can be implemented by any class. @@ -395,37 +406,40 @@ With all object interactions, follow the pattern of: (1) create the object, (2) use the object, (3) then free the object from memory. */ -MyClass *classVar = [MyClass alloc]; // alloc sets classVar's reference count to one. Returns pointer to object. +MyClass *classVar = [MyClass alloc]; // 'alloc' sets classVar's reference count to one. Returns pointer to object. [classVar release]; // Decrements classVar's reference count. -// retain claims ownership of existing object instance and increments reference count. Returns pointer to object. +// 'retain' claims ownership of existing object instance and increments reference count. Returns pointer to object. MyClass *newVar = [classVar retain]; // If classVar is released, object is still in memory because newVar is owner. [classVar autorelease]; // Removes ownership of object at end of @autoreleasepool block. Returns pointer to object. -// @property can use retain or assign as well for small convenient definitions. +// @property can use 'retain' and 'assign' as well for small convenient definitions. @property (retain) MyClass *instance; // Release old value and retain a new one (strong reference). @property (assign) NSSet *set; // Pointer to new value without retaining/releasing old (weak reference). +// Automatic Reference Counting (ARC) // Because memory management can be a pain, Xcode 4.2 and iOS 4 introduced Automatic Reference Counting (ARC). // ARC is a compiler feature that inserts retain, release, and autorelease automatically for you, so when using ARC, // you must not use retain, relase, or autorelease. -MyClass *arcMyClass = [[MyClass alloc] init]; // Without ARC, you will need to call: [arcMyClass release] after -// you're done using arcMyClass. But with ARC, there is no need. It will insert this release statement for you. +MyClass *arcMyClass = [[MyClass alloc] init]; +// ... code using arcMyClass +// Without ARC, you will need to call: [arcMyClass release] after you're done using arcMyClass. But with ARC, +// there is no need. It will insert this release statement for you. -// As for the "assign" and "retain" @property attributes, with ARC you use "weak" and "strong". -@property (weak) MyClass *weakVar; // weak does not take ownership of object. If original instance's reference count +// As for the 'assign' and 'retain' @property attributes, with ARC you use 'weak' and 'strong'. +@property (weak) MyClass *weakVar; // 'weak' does not take ownership of object. If original instance's reference count // is set to zero, weakVar will automatically receive value of nil to avoid application crashing. -@property (strong) MyClass *strongVar; // strong takes ownership of object. Ensures object will stay in memory to use. +@property (strong) MyClass *strongVar; // 'strong' takes ownership of object. Ensures object will stay in memory to use. // For regular variables (not @property declared variables), use the following: __strong NSString *strongString; // Default. Variable is retained in memory until it leaves it's scope. __weak NSSet *weakSet; // Weak reference to existing object. When existing object is released, weakSet is set to nil. -__unsafe_unretained NSArray *unsafeArray; // Like __weak but unsafeArray not set to nil when existing object is released. +__unsafe_unretained NSArray *unsafeArray; // Like __weak, but unsafeArray not set to nil when existing object is released. ``` ## Further Reading [Wikipedia Objective-C](http://en.wikipedia.org/wiki/Objective-C) -[Learning Objective-C](http://developer.apple.com/library/ios/referencelibrary/GettingStarted/Learning_Objective-C_A_Primer/) +[Programming with Objective-C. Apple PDF book](https://developer.apple.com/library/ios/documentation/cocoa/conceptual/ProgrammingWithObjectiveC/ProgrammingWithObjectiveC.pdf) [iOS For High School Students: Getting Started](http://www.raywenderlich.com/5600/ios-for-high-school-students-getting-started) |