ObservableViewController.swift

// MARK: - Init

deinit {
    NotificationCenter.default.removeObserver(self)
}

// MARK: - View Life Cycle

override func viewDidLoad() {
    super.viewDidLoad()
    addObservers()
}

// MARK: - Add Observers

private func addObservers() {
    NotificationCenter.default.addObserver(
        forName: .SomethingToObserveNotification,
        object: nil,
        queue: .main,
        completion: handleNotification
    )
}

private func handleNotification(_ notification: Notification) {
    // No-op but there is a leak in this controller!
}