Use of background/foreground methods in AppDelegate

Each object receive a UIApplicationDidEnterBackgroundNotification notification when the app goes in background. So to run some code when the app goes in background, you just have to listen to that notification where you want :

[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(appHasGoneInBackground:)
                                             name:UIApplicationDidEnterBackgroundNotification
                                           object:nil];

Don’t forget to release the listener when you don’t need to listen to it anymore :

[[NSNotificationCenter defaultCenter] removeObserver:self];

And best of the best, you can play the same way with the following notifications :

• UIApplicationDidEnterBackgroundNotification
• UIApplicationWillEnterForegroundNotification
• UIApplicationWillResignActiveNotification
• UIApplicationDidBecomeActiveNotification