Returns the receiver.
- iOS 2.0+
- macOS 10.0+
- tvOS 9.0+
- watchOS 2.0+
- Objective-C Runtime
The memory zone in which to create the copy of the receiver.
This method exists so class objects can be used in situations where you need an object that conforms to the
NSMutable protocol. For example, this method lets you use a class object as a key to an
NSDictionary object. You should not override this method.