Andy Jacobs blog

- (void)addObserver:(id)notificationObserver selector:(SEL)notificationSelector name:(NSString *)notificationName object:(id)notificationSender
- (void)postNotificationName:(NSString *)notificationName object:(id)notificationSender userInfo:(NSDictionary *)userInfo
- (void)removeObserver:(id)notificationObserver name:(NSString *)notificationName object:(id)notificationSender

//AppDelegate.m
- (void)applicationDidFinishLaunching:(UIApplication *)application {
       //….
       [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handler:) name:@"event" object:nil];
}
-(void)handler:(NSNotification *)notification
{
       NSLog(@"%@",notification);
       //will output:
       //NSConcreteNotification 0x574ef0 {name = event; object = <rootViewController: 0x580530>}
}
 
//RootViewController.m
- (void)viewDidLoad {
       //…
       [[NSNotificationCenter defaultCenter] postNotificationName:@"event" object:self];
}