CAAction protocol provides an interface that allows an object to respond to an action triggered by an
CALayer. When queried with an action identifier (a key path, an external action name, or a predefined action identifier) the layer returns the appropriate action object–which must implement the
CAAction protocol–and sends it a
Called to trigger the action specified by the identifier.
The identifier of the action. The identifier may be a key or key path relative to
anObject, an arbitrary external action, or one of the action identifiers defined in CALayer Class Reference.
The layer on which the action should occur.
A dictionary containing parameters associated with this event. May be
Available in iOS 2.0 and later.