title: Swift UIDatePicker doesn't show initial value
body: <p>I have a <code>UITextField</code> that uses a <code>UIDatePicker</code> as its input method as so:</p>
  
  <pre><code>lazy var starttime_text_field: UITextField = {
      let text_field = UITextField()
      ...
  
      let date_picker = UIDatePicker()
      date_picker.minimumDate = Date()
      date_picker.maximumDate = Calendar.current.date(byAdding: .day, value: 1, to: Date())
  
      date_picker.datePickerMode = .dateAndTime
      date_picker.addTarget(self, action: #selector(handleStarttimePicker(sender:)), for: .valueChanged)
      text_field.inputView = date_picker
  
      ...
      return text_field
  }()
  </code></pre>
  
  <p>When I select the text field, I would like for the first date that shows up in the picker to appear as the text field's text. However, that doesn't happen; only when I scroll through the picker does the picker's value appear in the text field. I've tried changing <code>.valueChanged</code> to other things, but I still haven't gotten it to work. How can I achieve this behavior? Thanks.</p>