Message flow in Objective-C

Does anyone have a good reference which really outlines how this entire 'message flow' between classes, subclasses, etc.... works in Objective-C? It seems very central to the architecture of the programming environment in Mac world and would be very help开发者_开发百科ful to understand.

This has been covered in a number of different questions, though to answer different aspects of the question.

This question/answer, in particular, seems relevant:

Objective-C: difference between id and void *

If you are curious as to exactly what happens at a method callsite, I wrote quite the long winded multi-part article giving an instruction-by-instruction tour of objc_msgSend().