IOS 5 Responding to Application Events

//ios 5
//responding to application level events

- (void)viewDidLoad
{
    [super viewDidLoad];
    [[NSNotificationCenter defaultCenter]
     addObserver:self
     selector:@selector(willEnterForegroundNotification:)
     name:UIApplicationWillEnterForegroundNotification
     object:nil];

    [[NSNotificationCenter defaultCenter]
     addObserver:self
     selector:@selector(willResignActiveNotification:)
     name:UIApplicationWillResignActiveNotification
     object:nil];

    // Do any additional setup after loading the view.
}
- (void)willEnterForegroundNotification:(NSNotification *)notification
{
    //app is returning to foreground from background
}

- (void)willResignActiveNotification:(NSNotification *)notification
{
    //home button is pressed
}