compatibility_alias

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This is a feature of the Objective-C compiler rather than of the runtime, anyway since it is documented nowhere and its existence was forgotten, we are documenting it here.

The keyword @compatibility_alias allows you to define a class name as equivalent to another class name. For example:

@compatibility_alias WOApplication GSWApplication;

tells the compiler that each time it encounters WOApplication as a class name, it should replace it with GSWApplication (that is, WOApplication is just an alias for GSWApplication).

There are some constraints on how this can be used--

• WOApplication (the alias) must not be an existing class;

• GSWApplication (the real class) must be an existing class.