Learning Swift™ Programming

Delegation

Delegation is one of the most powerful features of protocols. Delegation is not special to Swift or Objective-C. It is a design pattern, a reusable solution to a common problem within a certain context. A friend of mine described delegation best without even knowing it. He said, “Doesn’t a protocol allow you to send messages to anyone who implements that protocol?” Sort of. If you create a new iOS project, the first thing you will most likely see is the AppDelegate, which notifies you when certain things happen. For example, in AppDelegate there is a method called applicationWillTerminate. This method gets called when the application is about to be shut down. It can be called because it adopts UIApplicationDelegate. Let’s look at ...