@IBOutlet weak var oneTimeCodeView: OneTimeCodeView!

    override func viewDidAppear(_ animated: Bool) {
       // required:
      self.oneTimeCodeView.configure(countOfDigits: NUMBER_COUNT)
      self.oneTimeCodeView.didEnterLastDigit = { [weak self] (code) -> () in
          print(code)
          // TODO verify the code
      }
    }

    // (optional) if you want to clear OneTimeCodeView if verification fails
    func onVerificationError(error: Error) {
        self.oneTimeCodeView.clear()
        // display an error message
    }