title: UITextField with DatePicker crashes
body: <p>I am new to iOS/Swift so please bear with me.</p>
  
  <p>I have a TextField, timeTextField, and want to display a TimePicker on click. All this is working property but when another element is selected the app crashes why does it crash?
  <strong>UPDATE 1: updated code</strong>
  code:</p>
  
  <pre><code>func setupTimePicker(){
      datePickerView.datePickerMode = UIDatePickerMode.time
      datePickerView.removeFromSuperview()
      timeTextField.inputView = datePickerView
      datePickerView.addTarget(self, action: #selector(self.datePickerValueChanged(sender:)), for: .valueChanged)
  }
  
  func datePickerValueChanged(sender:UIDatePicker) {
      var date = Date()
      let calendar = Calendar.current
  
      date = sender.date;
  
      let hour = calendar.component(.hour, from: date)
      let minutes = calendar.component(.minute, from: date)
  
      timeTextField.text = String(format: "%02d", hour) + ":" + String(format: "%02d", minutes)
  }
  </code></pre>
  
  <p>error:</p>
  
  <blockquote>
    <p>[TestApp.ViewController pickTime:]: unrecognized selector sent to instance 0x7f9305e08e20</p>
  </blockquote>