TypedNotification

The TypedNotification microframework allows you to use NotificationCenter to post and receive strongly-typed notifications with associated data, without having to manually pack and unpack a userInfo dictionary.

Using a typed notification is simple. First, define a notification type:

struct MyNotification: TypedNotification {
    var value: String
}

Next, use NotificationCenter to add an observer for that notification:

class MyViewController: UIViewController {
    private var token: NotificationToken?

    override func viewDidLoad() {
        super.viewDidLoad()

        token = NotificationCenter.default.addObserver(for: MyNotification.self) { [weak self] (notification) in
            self?.received(notification)
        }
    }

    private func received(_ notification: MyNotification) {
        print(notification.value)
    }
}

In the example, MyViewController retains the NotificationToken returned by NotificationCenter.addObserver(). When the MyViewController instance is deallocated, the NotificationToken is deallocated and the observer is deregistered. The [weak self] capture list is important. Without it, there will be a retain cycle causing a memory leak.

Finally, use NotificationCenter to post notifications:

NotificationCenter.default.post(MyNotification(value: "foobar"), from: self)