Objective-C : Posing
we learn how to add methods from outside the class : Objective-C : Categories
Objective-C permits a class to wholly replace another class
within a program. The replacing class is said to "pose as" the target
Note: Class posing was declared deprecated with Mac OS X
v10.5, and is unavailable in the 64-bit runtime.
For the versions still supporting posing, all messages sent
to the target class are instead received by the posing class. There are several
•A class may only pose as one of its direct or indirect
•The posing class must not define any new instance variables
that are absent from the target class (though it may define or override
•The target class may not have received any messages prior
to the posing.
•Posing, similarly with categories, allows global
augmentation of existing classes. Posing permits two features absent from
•A posing class can call overridden methods through super,
thus incorporating the implementation of the target class.
•A posing class can override methods defined in categories
@interface CustomNSApplication : NSApplication
- (void) setMainMenu: (NSMenu*) menu
// do something with menu
class_poseAs ([CustomNSApplication class], [NSApplication class]);
This intercepts every invocation of setMainMenu to NSApplication.