An application can handle different kind of events thanks to responder objects. These objects implement specific methods that are useful to respond to one or more events. The
UIResponder class is the base class where an interface for these events is defined; therefore, most of the classes that are directly exposed to user interaction are subclasses of
UIResponder, such as
UIControl, and even the
A touch event is propagated through the application structure following an explicit path: the event is generated by the system and added into the event queue; the
UIApplication singleton gets the topmost event and propagates it to the key window that, in turn, identifies the view where the touch ...