override func viewDidLoad() {
    super.viewDidLoad()
        self.scanner.resultBlock = { [weak self] code in
        print(code)
        self?.navigationController?.popViewController(animated: true)
    }
}

@IBOutlet weak var scanner: QRCodeScannerView!

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    self.scanner.start()
}

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    self.scanner.stop()
}