问题
Does objective-c offer a way to intercept calls to class method that does not exist?
回答1:
The forwardInvocation method is what you are going to want to use. It is called automatically when a non-existent selector is called on an object. The default behavior of this method is to call doesNotRecognizeSelector:(which is what outputs debug information to your console), but you can override it do anything you want. One recommended approach by Apple is to have this method forward the method invocation to another object.
- (void)forwardInvocation:(NSInvocation *)anInvocation
Note that forwardInvocation is a fairly expensive operation. An NSInvocation object needs to be created by the framework and (optionally) used to invoke a selector on another instance. If you are looking for a (relatively) faster method of detecting non-existent selectors then you can choose to implement forwardingTargetForSelector instead.
- (id)forwardingTargetForSelector:(SEL)aSelector
You should Apple's documentation for how to override these methods effectively, there are some gotcha's to watch out for, particularly when overriding the forwardInvocation method on the same object that will have the missing selectors.
回答2:
Yes, you can with the resolveClassMethod: class method (which is defined on NSObject):
http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSObject_Class/Reference/Reference.html
Here is also something to watch out for (stumped me the first time): http://iphonedevelopment.blogspot.com/2008/08/dynamically-adding-class-objects.html
来源：https://stackoverflow.com/questions/6939284/objective-c-and-magic-methods-in-class