How do I test whether an object is an instance of a particular class in Objective-C? Let’s say I want to see if object a is an instance of class b, or class c, how do I go about doing it?

How do I test whether an object is an instance of a particular class in Objective-C? Let’s say I want to see if object a is an instance of class b, or class c, how do I go about doing it?