Basics of Notifications with NSNotificationCenter

What follows is a brief guide to working with Notifications in Cocoa. I’ll cover the basics, including registering an observer and posting notifications, just enough to start using notifications in your iPhone apps.

There is an instance of NSNotificationCenter available to every running iPhone application. This class acts as an intermediary to facilitate communication between objects that are interested in being notified at some point in the future (these objects are known as the observers) and a poster that posts to the notification center, resulting in all observers (registered for a specific notification) being called.
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