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| -rw-r--r-- | objective-c.html.markdown | 152 |
1 files changed, 1 insertions, 151 deletions
diff --git a/objective-c.html.markdown b/objective-c.html.markdown index 348a72d5..772e72ca 100644 --- a/objective-c.html.markdown +++ b/objective-c.html.markdown @@ -552,116 +552,6 @@ int main (int argc, const char * argv[]) { NSLog(@"Car locked."); // Instances of Car can't use lockCar because it's not in the @interface. } -// Categories -// A category is a group of methods designed to extend a class. They allow you to add new methods -// to an existing class for organizational purposes. This is not to be mistaken with subclasses. -// Subclasses are meant to CHANGE functionality of an object while categories instead ADD -// functionality to an object. -// Categories allow you to: -// -- Add methods to an existing class for organizational purposes. -// -- Allow you to extend Objective-C object classes (ex: NSString) to add your own methods. -// -- Add ability to create protected and private methods to classes. -// NOTE: Do not override methods of the base class in a category even though you have the ability -// to. Overriding methods may cause compiler errors later between different categories and it -// ruins the purpose of categories to only ADD functionality. Subclass instead to override methods. - -// Here is a simple Car base class. -@interface Car : NSObject - -@property NSString *make; -@property NSString *color; - -- (void)turnOn; -- (void)accelerate; - -@end - -// And the simple Car base class implementation: -#import "Car.h" - -@implementation Car - -@synthesize make = _make; -@synthesize color = _color; - -- (void)turnOn { - NSLog(@"Car is on."); -} -- (void)accelerate { - NSLog(@"Accelerating."); -} - -@end - -// Now, if we wanted to create a Truck object, we would instead create a subclass of Car as it would -// be changing the functionality of the Car to behave like a truck. But lets say we want to just add -// functionality to this existing Car. A good example would be to clean the car. So we would create -// a category to add these cleaning methods: -// @interface filename: Car+Clean.h (BaseClassName+CategoryName.h) -#import "Car.h" // Make sure to import base class to extend. - -@interface Car (Clean) // The category name is inside () following the name of the base class. - -- (void)washWindows; // Names of the new methods we are adding to our Car object. -- (void)wax; - -@end - -// @implementation filename: Car+Clean.m (BaseClassName+CategoryName.m) -#import "Car+Clean.h" // Import the Clean category's @interface file. - -@implementation Car (Clean) - -- (void)washWindows { - NSLog(@"Windows washed."); -} -- (void)wax { - NSLog(@"Waxed."); -} - -@end - -// Any Car object instance has the ability to use a category. All they need to do is import it: -#import "Car+Clean.h" // Import as many different categories as you want to use. -#import "Car.h" // Also need to import base class to use it's original functionality. - -int main (int argc, const char * argv[]) { - @autoreleasepool { - Car *mustang = [[Car alloc] init]; - mustang.color = @"Red"; - mustang.make = @"Ford"; - - [mustang turnOn]; // Use methods from base Car class. - [mustang washWindows]; // Use methods from Car's Clean category. - } - return 0; -} - -// Objective-C does not have protected method declarations but you can simulate them. -// Create a category containing all of the protected methods, then import it ONLY into the -// @implementation file of a class belonging to the Car class: -@interface Car (Protected) // Naming category 'Protected' to remember methods are protected. - -- (void)lockCar; // Methods listed here may only be created by Car objects. - -@end -//To use protected methods, import the category, then implement the methods: -#import "Car+Protected.h" // Remember, import in the @implementation file only. - -@implementation Car - -- (void)lockCar { - NSLog(@"Car locked."); // Instances of Car can't use lockCar because it's not in the @interface. -} - -@end - -// Protocols -// A protocol declares methods that can be implemented by any class. -// Protocols are not classes themselves. They simply define an interface -// that other objects are responsible for implementing. -@protocol MyProtocol - - (void)myProtocolMethod; @end /////////////////////////////////////// @@ -760,47 +650,7 @@ if ([myClass conformsToProtocol:@protocol(CarUtilities)]) { - (void)beNiceToBrother:(id <Brother>)brother; @end -// The @implementation needs to implement the @properties and methods for the protocol. -@implementation Car : NSObject <CarUtilities> - -@synthesize engineOn = _engineOn; // Create a @synthesize statement for the engineOn @property. - -- (void)turnOnEngine { // Implement turnOnEngine however you would like. Protocols do not define - _engineOn = YES; // how you implement a method, it just requires that you do implement it. -} -// You may use a protocol as data as you know what methods and variables it has implemented. -- (void)turnOnEngineWithCarUtilities:(id <CarUtilities>)objectOfSomeKind { - [objectOfSomeKind engineOn]; // You have access to object variables - [objectOfSomeKind turnOnEngine]; // and the methods inside. - [objectOfSomeKind engineOn]; // May or may not be YES. Class implements it however it wants. -} - -@end -// Instances of Car now have access to the protocol. -Car *carInstance = [[Car alloc] init]; -[[carInstance setEngineOn:NO]; -[carInstance turnOnEngine]; -if ([carInstance engineOn]) { - NSLog(@"Car engine is on."); // prints => "Car engine is on." -} -// Make sure to check if an object of type 'id' implements a protocol before calling protocol methods: -if ([myClass conformsToProtocol:@protocol(CarUtilities)]) { - NSLog(@"This does not run as the MyClass class does not implement the CarUtilities protocol."); -} else if ([carInstance conformsToProtocol:@protocol(CarUtilities)]) { - NSLog(@"This does run as the Car class implements the CarUtilities protocol."); -} -// Categories may implement protocols as well: @interface Car (CarCategory) <CarUtilities> -// You may implement many protocols: @interface Car : NSObject <CarUtilities, CarCleaning> -// NOTE: If two or more protocols rely on each other, make sure to forward-declare them: -#import "Brother.h" -@protocol Brother; // Forward-declare statement. Without it, compiler would through error. - -@protocol Sister <NSObject> - -- (void)beNiceToBrother:(id <Brother>)brother; - -@end // See the problem is that Sister relies on Brother, and Brother relies on Sister. #import "Sister.h" @@ -816,7 +666,7 @@ if ([myClass conformsToProtocol:@protocol(CarUtilities)]) { /////////////////////////////////////// // Blocks /////////////////////////////////////// -// Blocks are statements of code, just like a function, that is able to be used as data. +// Blocks are statements of code, just like a function, that are able to be used as data. // Below is a simple block with an integer argument that returns the argument plus 4. int (^addUp)(int n); // Declare a variable to store the block. void (^noParameterBlockVar)(void); // Example variable declaration of block with no arguments. |