iOS Programming: The Big Nerd Ranch Guide

The View Hierarchy

Every application has a single instance of UIWindow that serves as the container for all the views in the application. The window is created when the application launches. Once the window is created, you can add other views to it.

When a view is added to the window, it is said to be a subview of the window. Views that are subviews of the window can also have subviews, and the result is a hierarchy of view objects with the window at its root.

Figure 4.3  An example view hierarchy and the interface that it creates

Once the view hierarchy has been created, it will be drawn to the screen. This process ...