How to update a UITextField when receiving input from a UIPickerView?

问题

Currently, I am programmatically creating a UITextField and UIPickerView within cellForRowAt. I can easily update the selected UIPickerView value within didSelectRow if I connect my UITextField to an IBOutlet.

However, I require the UITextField to be created programmatically with applied AutoLayout constraints.

However, I don't know how to update the UITextField as I have no reference to it in the UIPickerView's didSelectRow function since it's created programmatically within cellForRowAt like so:

var testing: [String] = []

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell
{
    // Dequeue the cell to load data
    let cell: UITableViewCell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)

    if indexPath.section == 2
    {
        let wearsPickerView: UIPickerView = UIPickerView()

        wearsPickerView.delegate = self
        wearsPickerView.dataSource = self

        let textField: UITextField = UITextField()

        textField.translatesAutoresizingMaskIntoConstraints = false

        textField.textColor = UIColor.black

        textField.text = "Test"

        textField.delegate = self
        textField.inputView = wearsPickerView

        cell.contentView.addSubview(textField)

        let leadingConstraint = NSLayoutConstraint(item: cell.contentView, attribute: NSLayoutAttribute.leading, relatedBy: NSLayoutRelation.equal, toItem: textField, attribute: NSLayoutAttribute.leading, multiplier: 1.0, constant: 0)
        let trailingConstraint = NSLayoutConstraint(item: cell.contentView, attribute: NSLayoutAttribute.trailing, relatedBy: NSLayoutRelation.equal, toItem: textField, attribute: NSLayoutAttribute.trailing, multiplier: 1.0, constant: 0)
        cell.contentView.addConstraint(leadingConstraint)
        cell.contentView.addConstraint(trailingConstraint)

        let topConstraint = NSLayoutConstraint(item: cell.contentView, attribute: NSLayoutAttribute.top, relatedBy: NSLayoutRelation.equal, toItem: textField, attribute: NSLayoutAttribute.top, multiplier: 1.0, constant: 0)
        let bottomConstraint = NSLayoutConstraint(item: cell.contentView, attribute: NSLayoutAttribute.bottom, relatedBy: NSLayoutRelation.equal, toItem: textField, attribute: NSLayoutAttribute.bottom, multiplier: 1.0, constant: 0)
        cell.contentView.addConstraint(topConstraint)
        cell.contentView.addConstraint(bottomConstraint)
    }

    return cell
}

func textFieldShouldReturn(_ textField: UITextField) -> Bool
{
    textField.resignFirstResponder()

    return true
}

func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int
{
    return testing.count
}

func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String?
{
    return testing[row]
}

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int)
{
    // How to update UITextField string?

}

回答1:

You can get the cell for the corresponding index path, and find the textfield in that cell. You have 2 options for finding the textField. One would be to use tags, in case you had more than one UITextFields in that cell, which you don't. So you can do it like this:

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int)
  {
    // choose the correct row. I've assumed you only have one row.
    if let cell = tableView.cellForRow(at: IndexPath(row: 0, section: 2)) {
      for subview in cell.subviews {
        if let textField = subview as? UITextField {
          textField.text = testing[row]
          break
        }
      }
    }
  }

来源：https://stackoverflow.com/questions/43087400/how-to-update-a-uitextfield-when-receiving-input-from-a-uipickerview