何时使用（或不使用）代表

This is a pretty general question, but I was wondering today about delegates. At this point I don't really have a specific time I do use them or don't use them - aside from obvious cases, like passing selections from a picker or tableview stuff. For example, if there's a situation where I can pass a reference to an object around and use that to call methods, is there a reason to implement a delegate? In summary, what is the delegate pattern intended for use in and when is it better to NOT use it?This is a pretty general question, but I was wo