The starting point for the application – the app must have one.
Manages a single top level UIWindow.
Called right before the app is ready for the user – your chance to prepare the application for action before the user can do anything.
xib doc window
An instance of UIApplication – manages the event queue for your application
Can be ignored for iOS
Subclass of NSObject created by Xcode for this project – this is where you edit the source code for this class.
An instance of UIWindow which represents the applications only window.
Interface Builder Windows Used To Design
Library and Inspector needed all the time.
Visible to the user.
Hold data and know nothing about the UI.
Keep the view and model objects in sync, control application flow and save model objects out to the filesystem. The default for a new application is 'AppDelegate'.