Declaring Objective-C Types

From: cast.m

 6 NSMutableArray *mutableArray = [NSMutableArray
        new];
 7 NSArray *array = mutableArray;
 8 NSObject *object = array;
 9 id obj = mutableArray;
10 mutableArray = (NSMutableArray*)object;
11 mutableArray = obj;

Objective-C, as its name implies, adds objects to C. Specifically, objects following the Smalltalk model, which are instances of classes. Objects are always allocated on the heap and so are always referenced by pointer.