Is it possible to downgrade an object in objective c to its superclass?

Question

If I have an instance of class B which is a subclass of class A, is there a way for me to turn my instance of class B into an instance of class A without explicitly writing code to do it?

I do not mean simply downcasting with the standard c syntax.

Answer 1

You may be able to do this with the objc runtime (see the object_setClass(id object, Class cls) in the Objective-C runtime reference. The more important point, however, is that you almost certainly do not want to do this. If your subclass does not follow the Liskov Substituion Principle, it shouldn't be a subclass (i.e. an inheritance relationship is not appropriate and you should choose some other design). You can always invoke the superclass' method implementations with [super someMethod] from within your subclass.