Xcode 5 Start to Finish: iOS and OS X Development

The Controllers

iOS applications are organized around a sequence of view controllers, objects derived from UIViewController. Each view controller mediates between model objects and the views that fill the device’s screen. For each full-screen view you see in the sketch, you must provide a UIViewController subclass to link the data in the model to the views on the screen. In the life cycle of a view, the controller comes first; when it is initialized, it creates or loads the view objects and sets them up to reflect the model.

Now, even a simple application like this slides four main views onto and off of the screen, according to a precise hierarchy. Managing the relationships between them—which to slide in, which to slide back to—would seem to ...