Programming iOS 4

Automatic Popovers

In a few situations, the framework will automatically create and display a popover for you. I am not personally fond of this behavior; the advantages of the automatic behavior (such as the fact that you do not have to provide code to create the popover) are counterbalanced, in my view, by the disadvantages — in particular, you can’t get access to the UIPopoverController, so the behavior and appearance of the popover is completely out of your hands.

One such situation is what happens when a search bar (a UISearchBar) tied to a search display controller (UISearchDisplayController) appears in a toolbar (UIToolbar) on the iPad. I’ll illustrate by rewriting the search bar code from Chapter 21. In this example, there’s a toolbar at the top of the screen, and in the nib editor we drag a search bar and search display controller (a single item in the Object library) into that toolbar. This single move puts a search bar in a bar button item into the toolbar and creates a search display controller at the nib’s top level, and configures all connections automatically, as follows:

• The search bar’s delegate is the File’s Owner.
• The File’s Owner’s searchDisplayController is the search display controller. This is a UIViewController property that I didn’t mention in Chapter 21, because its worth is not clear when a UISearchDisplayController is created and configured in code. When a UISearchDisplayController is instantiated from a nib, however, this property is an outlet that retains ...