Is there a design pattern that deals with callback mechanism?

Question

Is there a design pattern that deals with callback mechanism?

Answer 1

It depends on how the callback is used.

Design patterns are all about communicating your intent.

If you intended to allow one or more callbacks to be registered and they can be called as notification "at some point in the future", you're talking Observer. Also -- the actual invocation of the callback in this case is usually "optional" or triggered based on some stimulus. (The callbacks may or may not ever be called)

If you intended to pass in "something to do", and that gets done in the method (or is used to "do something" during a later process) you're talking Strategy. Also -- the actual invocation usually happens.

Note that the exact same code could be either -- it's really about how you're thinking about the problem and how you want others to think about it.