NSNotification in iphone sdk

Question

what is the use of NSNotification in iphone sdk?

Thanks

Answer 1

I know this isn't generally a good way to answer questions, but RTFM.

NSNotification objects encapsulate information so that it can be broadcast to other objects by an NSNotificationCenter object. An NSNotification object (referred to as a notification) contains a name, an object, and an optional dictionary. The name is a tag identifying the notification. The object is any object that the poster of the notification wants to send to observers of that notification (typically, it is the object that posted the notification). The dictionary stores other related objects, if any. NSNotification objects are immutable objects.

You can create a notification object with the class methods notificationWithName:object: or notificationWithName:object:userInfo:. However, you don’t usually create your own notifications directly. The NSNotificationCenter methods postNotificationName:object: and postNotificationName:object:userInfo: allow you to conveniently post a notification without creating it first.

Answer 2

You should have a look at the Notifications section in the Cocoa Fundamentals Guide. There's anything you need to know about notifications there : from definition to use cases.