Programming iOS 6, 3rd Edition

Managing a Popover

Unlike a presented view controller or a child view controller, a UIPopoverController instance is not automatically retained for you by some presenting view controller or parent view controller; you must retain it yourself. If you fail to do this, then if the UIPopoverController goes out of existence while its popover is on the screen, your app will crash (with a helpful message: “-[UIPopoverController dealloc] reached while popover is still visible”). Also, you might need the retained reference to the UIPopoverController later, when the time comes to dismiss the popover.

There are actually two ways in which a popover can be dismissed: the user can tap outside the popover, or you can explicitly dismiss the popover (as I do with the first popover in Figure 22-1 when the user taps the Done button or the Cancel button). In order to dismiss the popover explicitly, you send its UIPopoverController the dismissPopoverAnimated: message. Obviously, then, you need a reference to the UIPopoverController.

Even if a popover is normally dismissed automatically by the user tapping outside it, you still might want to dismiss it explicitly on certain occasions — so you still might need a reference to the popover controller. For example, in keeping with the transient nature of popovers, I like to dismiss the current popover programmatically when the application undergoes certain strong transitions, such as going into the background or being rotated. (See also Apple’s technical note ...