Consequences

The Delegates pattern dramatically reduces the need to subclass Cocoa objects to implement application-specific behavior. Many of the more complex Cocoa classes such as NSApplication, NSBrowser, NSTableView, NSText, and NSWindow are rarely if ever subclassed because the Delegates pattern provides a better alternative.

The Delegates pattern reduces the coupling between objects. Subclassing creates the tightest possible coupling between the subclass and its superclass. The Delegates pattern substitutes a much looser relationship based on anonymous objects. The coupling between an object and its delegate is so loose that the object can function without any delegate at all, and a delegate is free to implement any subset of the potential delegate methods.