Delegation at its root is a very simple concept. You can make dinner all by yourself or you can delegate the cooking to your deadbeat friends lazing on the couch. You can buy all the party supplies yourself or you can delegate buying the drinks to your brother and getting the decorations to your sister. You can build an app all by yourself or you can delegate the user interface to your designer friend while you code under the hood.
Delegation on the iPhone OS is no different. Rather than creating a single class with many responsibilities, you can share responsibility among several classes. Delegation makes classes more reusable and maintainable. Many UIKit classes allow customization of their behavior via delegation.
A delegate ...