You have to create an instance of that class and keep it alive in memory, something like:
UIViewController *myViewController = [[UIViewController alloc] init];
[[NSNotificationCenter defaultCenter] addObserver:myViewController
selector:@selector(NotificationReceived:)
name:@"notification"
object:nil];
And remember to un-register observer before the observer is deallocated, else your app will crash
Or in Swift 3:
let myViewController = UIViewController()
NotificationCenter.default.addObserver(
myViewController,
selector: #selector(NotificationReceived),
name: Notification.Name("notification"),
object: nil)