CODEWITHSUNDEEP
iphone
carthee
carthee

Reputation: 110

NSNotification in iphone sdk

what is the use of NSNotification in iphone sdk?

Thanks

Upvotes: 0

Views: 1822

Answers (5)

Sam Baumgarten
Sam Baumgarten

Reputation: 2249

NSNotifications allow you to have a method called when a event occurs. For example if you have a MPMoviePlayer and you want todo something when it is done you could use the following code:
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(movieFinished:) name:MPMoviePlayerPlaybackDidFinishNotification object:yourMoviePlayer.moviePlayer];

or if you want to do something when the device rotates:
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(orientationChanged:) name:UIDeviceOrientationDidChangeNotification object:self];

Upvotes: 1

Sam Baumgarten
Sam Baumgarten

Reputation: 2249

You register a UINotification when you want to receive a alert from iOS. So if you want to do something when a accessory is plugged in or a TV is plugged in you would register a UINotification for it and it would call a method in your app when the event occurs.

Upvotes: 0

hennes
hennes

Reputation: 9342

In terms of events NSNotifications are an alternative to delegation. Delegation can be used to notify one single delegate of an event, whereas notifications can be used to notify an arbitrary number of receivers. A notification is sent to the main notification center, which then notifies every object, that has registered for the notification.

One important difference is, that with delegation you can receive the delegates response to the event, whereas with NSNotifications you just send away the notification, but you don't know about the receivers or their response to the notification.

Upvotes: 0

David
David

Reputation: 998

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.

Upvotes: 0

jtbandes
jtbandes

Reputation: 118651

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.

Upvotes: 3

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