当用户选择UITextField时,如何显示UIDatePicker而不是键盘？

let datePicker = UIDatePicker()
datePicker.datePickerMode = .date
datePicker.addTarget(self, action: #selector(datePickerValueChanged), for: .valueChanged)

let inputAccessoryView = UIView()
inputAccessoryView.frame = CGRect(x: 0, y: 0, width: view.bounds.width, height: 200)
inputAccessoryView.addSubview(datePicker)

textField.inputAccessoryView = inputAccessoryView

@objc func datePickerValueChanged(sender: UIDatePicker) {
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yyyy-MM-dd"
    textField.text = dateFormatter.string(from: sender.date)
}

override func inputAccessoryViewDidScroll() {
    textField.resignFirstResponder()
}