UIControl
UIControl is a subclass of UIView whose chief purpose is to be the superclass of several further built-in classes and to endow them with common behavior. These are classes representing views with which the user can interact (controls).
The most important thing that controls have in common is that they automatically track and analyze touch events (Chapter 18) and report them to your code as significant control events by way of action messages. Each control implements some subset of the possible control events. The full set of control events is listed under UIControlEvents in the Constants section of the UIControl class documentation:
-
UIControlEventTouchDown -
UIControlEventTouchDownRepeat -
UIControlEventTouchDragInside -
UIControlEventTouchDragOutside -
UIControlEventTouchDragEnter -
UIControlEventTouchDragExit -
UIControlEventTouchUpInside -
UIControlEventTouchUpOutside -
UIControlEventTouchCancel -
UIControlEventValueChanged -
UIControlEventEditingDidBegin -
UIControlEventEditingChanged -
UIControlEventEditingDidEnd -
UIControlEventEditingDidEndOnExit -
UIControlEventAllTouchEvents -
UIControlEventAllEditingEvents -
UIControlEventAllEvents
The control events also have informal names that are visible in the Connections inspector when you’re editing a nib. I’ll mostly use the informal names in the next couple of paragraphs.
Control events fall roughly into three groups: the user has touched the screen (Touch Down, Touch Drag Inside, Touch Up Inside, etc.), edited text (Editing Did Begin, ...
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