A navigation controller is good for moving through related scenes. But what if you have different functionality or different categories of scenes? For that, you want a navigation controller that switches between different kinds of content. This is what
A good example is the Clock app, shown in Figure 7-9. On the bottom of the app is a bar with four buttons, the tab bar. Each tab shows a different major function of Clock. Three of those areas have at least two screens: World Clock has a screen to add or edit a city, Alarm has one for adding or editing the details for an alarm, and Timer lets you specify a sound.
Each of the four areas has a different layout and performs different ...