class CountUpViewController: UIViewController {

    // ①Create Observable
    @MobS.Observable(value: 0)
    var count: Int

    @IBOutlet weak var countLabel: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()

        // ②Create Observer
        $count.addObserver(with: self) { (self, count) in
            self.countLabel.text = "\(count)"
        }
    }
    
    @IBAction func buttonTapped(_ sender: Any) {
        // ③Update Observable
        count += 1
    }

}