Does anything in Objective-C use associative references under the hood?

Question

Does anything in Objective-C use associative references under the hood? For example, do property setter and getter use it behind the scene?

Answer 1

No. That would be much too slow.

Some classes in Cocoa use them, but nothing in ObjC itself.

Answer 2

I would think associative references would be used explicitly by developers extending exiting classes. When the compiler generates getters and setters it has access to the source code.