UIPopoverControllerDelegate protocol defines the methods you can implement for the delegate of a
UIPopoverController object. Popover controllers notify their delegate whenever user interactions would cause the dismissal of the popover and, in some cases, give the user a chance to prevent that dismissal.
Responding to Popover Position Changes
Managing the Popover’s Dismissal
UIAccelerometerDelegate protocol defines a single method for receiving acceleration-related data from the system. Implementation of this method is optional, but expected.
For apps that run in versions of iOS prior to iOS 8, the
UIAlertViewDelegate protocol defines the methods a delegate of a
UIAlertView object should implement. The delegate implements the button actions and any other custom behavior. Some of the methods defined in this protocol are optional.