iOS: NSNotificationCenter

Receiver

- (void)viewDidDisappear:(BOOL)animated

{
    [[NSNotificationCenter defaultCenter] removeObserver:self];
    [super viewDidDisappear: animated];
}

- (void)viewWillAppear:(BOOL)animated

{

    [super viewWillAppear: animated];

    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(receiveNotification:) name:@"Notification" object:nil];
}

- (void) receiveNotification:(NSNotification *) notification
{
    // Do something
}

Somewhere in another class

[[NSNotificationCenter defaultCenter] postNotificationName:@"Notification" object:self];