Graphics Programs Reference
In-Depth Information
For the More Curious: View Controller Relationships
The relationships between view controllers are important for understanding where and how
a view controller's view appears on the screen. Overall, there are two different types of re-
lationships between view controllers: parent-child relationships and presenting-presenter
relationships. Let's look at each one individually.
Parent-child relationships
Parent-child relationships are formed when using view controller containers . Examples of
view controller containers are UINavigationController , UITabBarControl-
ler , and UISplitViewController (which you will see in Chapter 26 ) . You can
identify a view controller container because it has a viewControllers property that is
an array of the view controllers it contains.
A view controller container is always a subclass of UIViewController and thus has a
view . The behavior of a view controller container is that it adds the views of its
viewControllers as subviews of its own view. A container has its own built-in inter-
face, too. For example, a UINavigationController 's view shows a navigation bar
and the view of its topViewController .
View controllers in a parent-child relationship form a family . So, a UINavigationCon-
troller and its viewControllers are in the same family. A family can have mul-
tiple levels. For example, imagine a situation where a UITabBarController contains a
UINavigationController that contains a UIViewController . These three view
controllers are in the same family ( Figure 13.6 ). The container classes have access to their
children through the viewControllers array, and the children have access to their an-
cestors through four properties of UIViewController .
Figure 13.6 A view controller family
 
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