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== The Responder Chain ==

In the chapter entitled Understanding iPhone Views, Windows and the View Hierarchy we spent some time talking about the view hierarchy of an application’s user interface and how that hierarchy also defined part of the application’s responder chain. In order to fully understand the concepts behind the handling of touch screen gestures it is first necessary to spend a little more time learning about the responder chain.

== Touch Notification Methods ==

Touch screen events cause one of four methods on the first responder object to be called. The method that gets called for a specific event will depend on the nature of the interaction. In order to handle events, therefore, it is important to ensure that the appropriate methods from those outlined below are implemented within your responder chain. These methods will be used in the worked example contained in the iPhone Multitouch, Tap and Gesture Event Handling Tutorial chapter of this book: