Difference between class clusters and abstract factory in cocoa

Question

I have read that Obj-C class clusters are an implementation of the abstract factory .

Can anyone explain if there are any differences between the 2 as design patterns. I read somewhere that there are certain restrictions on class clusters that don't apply to traditional abstract factory but it did not give more details.

Answer 1

Most of the limitations concern attempting to modify the Foundation class clusters rather than those you may write on your own. For example, subclassing NSDictionary (which is a Foundation class cluster) can lead to some interesting problems.

You are free to implement your own class clusters, which is fairly easy and can have a high payoff. A class cluster is a type of abstract factory .