Can I use a class category to override a method that is already implemented using a category? Like this:
1) Original method
-(BOOL) method {
return true;
}
2) Overrided method
-(BOOL) method {
NSLog(@"error?");
return true;
}
Will this work, or is this illegal?
FromApple documentation:
Although the Objective-C language currently allows you to use a category to override methods the class inherits,or even methods declared in the class interface, you are strongly discouraged from doing so. A category is not a substitute for a subclass. There are several significant shortcomings to using a category to override methods:
When a category overrides an inherited method, the method in the category can, as usual, invoke the inherited implementation via a message tosuper. However,if a category overrides a method that exists in the category's class, there is no way to invoke the original implementation.
A category cannot reliably override methods declared in another category of the same class.
This issue is of particular significance because many of the Cocoa classes are implemented using categories. A framework-defined method you try to override may itself have been implemented in a category, and so which implementation takes precedence is not defined.
The very presence of some category methods may cause behavior changes across all frameworks. For example, if you override thewindowWillClose:delegate method in a category on NSObject, all window delegates in your program then respond using the category method; the behavior of all your instances of NSWindow may change. Categories you add on a framework class may cause mysterious changes in behavior and lead to crashes.
