View Controller Programming Guide for iOS

View controllers are a vital link between an app’s data and its visual appearance. Whenever an iOS app displays a user interface, the displayed content is managed by a view controller or a group of view controllers coordinating with each other. Therefore, view controllers provide the skeletal framework on which you build your apps.

iOS provides many built-in view controller classes to support standard user interface pieces, such as navigation and tab bars. As part of developing an app, you also implement one or more custom controllers to display the content specific to your app.