Source files. This is the typical extension used for source files and can contain both Objective-C and C code.
.mm
Source files. A source file with this extension can contain C++ code in addition to Objective-C and C code. This extension should be used only if you actually refer to C++ classes or features from your Objective-C code.
7 Class Interface
Class declaration in *.h
@interface MyClass : NSObject
{
int count;
id data;
NSString* name;
}
- (id)initWithString:(NSString*)aName;
+ (MyClass*)createMyClassWithString:(NSString*)aName //Class method;
@end
// message without argument
[receiver message];
// message with single argument
[receiver message: argument];
// message with multiple arguments
[receiver message: arg1 argument2: arg2];
// receiving a return value
int status = [receiver message];
// message with a variable number of arguments
[receiver makeGroup: group, memberOne, memberTwo, memberThree];
17 Object Messaging Examples
Sending messages to the class is the same as sending them to an instance, you only need to use the class name
// nil is essentially the same as NULL
NSMutableArray *myArray = nil;
// Create a new array and assign it to the myArray variable.
myArray = [NSMutableArray array];
18 Dynamic Typing
Supports strongly and weakly (dynamic) typed variable declarations
Person* myPerson; // Strong typing
id myObject; // Weak typing
Dynamic type id is completely unrestrictive
The type of an object is only determined at runtime
Allows for introspection and dynamic binding
19 Dynamic Binding
Supports (dynamic) binding of methods at runtime
Allows high flexible programming paradigms
//Dynamic binding example
@interface ClassA : NSObject {…}
- (void) doSomething;
@end
@interface ClassB : NSObject { …}
- (void) doSomething;
@end
// anywhere
id object = … // An object of an arbitrary class
[object doSomething]; // polymorph between ClassA und ClassB
20 Hands On Objective-C
Please open the terminal and create your first Objective-C project.
Exercise: Create a new Objective-C project that prints "Hello World" to the console
