How do I observe user editing a textField in an UIAlertController?

Question

I have an UIAlertController with a textField. Since I can't create an outlet for the textField I have to find another way to get ahold of a function that observes user input in realtime.

I have made some attempts, but not successfully. This thread explain how to add a target to the textField:

How do I check when a UITextField changes?

textfield.addTarget(self, action: #selector(ViewControllerr.textFieldDidChange(_:)), for: UIControl.Event.editingChanged)

I tried this, but don't quite understand the #selector input. Does it want my UIViewController? or my UIAlertController I tried both but got the same error message:

Value of type 'UIViewController' has no member 'textFieldDidChange'

Same with UIAlertController.

I also tried setting my textField to delegate to access functions of that class:

textField.delegate = self as? UITextFieldDelegate

But I guess this isn't the correct approach as I still couldn't access any functions except by doing:

textField.delegate?.textFieldDidBeginEditing?(textField)

But that didn't give me anything either.

I also tried adding an extension like this:

extension UITextFieldDelegate {
    func textFieldDidBeginEditing(_ textField: UITextField) {
        print("🦋EDITING")
}// became first responder

    func textFieldDidEndEditing(_ textField: UITextField) {
        print("🦋EDITING")
    }
}

But for some reason I can't access them through textView

If I extend the class like this:

extension PickNumberViewController: UITextFieldDelegate {...}

I get the same error message

Value of type 'UITextField' has no member 'textFieldDel...'

which makes no sense since I set textField to UITextFieldDelegate not UITextField.

Let me know if you would like to see my code as well.

Answer 1

iOS13+ One option is to use UIAction

extension UIAlertController {

public func addTextField(_ configuration: @escaping ((UITextField) -> Void),
                         onEditingDidBegin: ((UITextField) -> Void)? = nil,
                         onEditingChanged: ((UITextField) -> Void)? = nil,
                         onEditingDidEnd: ((UITextField) -> Void)? = nil) {
    self.addTextField { textField in
        configuration(textField)
        if let onEditingDidBegin {
            textField.addAction(UIAction { action in
                onEditingDidBegin(action.sender as! UITextField)
            }, for: .editingDidBegin)
        }
        if let onEditingChanged {
            textField.addAction( UIAction { action in
                onEditingChanged(action.sender as! UITextField)
            }, for: .editingChanged)
        }
        if let onEditingDidEnd {
            textField.addAction( UIAction { action in
                onEditingDidEnd(action.sender as! UITextField)
            }, for: .editingDidEnd)
        }
    }
}

Use like so:

let alert = UIAlertController(title: "Enter Text", message: nil, preferredStyle: .alert)
alert.addTextField { textField in
        textField.text = "Some text"
        textField.placeholder = "Placeholder"
    } onEditingDidBegin: { textField in
        textField.selectAll(nil) // selects all text
    } onEditingChanged: { textField in
        if let text = textField.text {
            textField.textColor = text.count > 5 ? .red : .label
        }
    } onEditingDidEnd: { textField in
        if let text = textField.text {
            if text.count > 5 {
                textField.text = "This is too long"
            }
        }
    }

You shouldn't use onEditingDidEnd for your final validation though. Put that in the UIAlertAction for your "OK" button and pull out the textFields:

let okAction = UIAlertAction(title: "OK", style: .destructive) { [weak self, weak alert] _ in
        if let self,
           let alert,
           let textField = alert.textFields?.first {
            // validate (here, 'self', is a view controller)
            self.label.text = textField.text
        }
}
alert.addAction(okAction)

Answer 2

You don't need to hold a reference to the text field. You can add target or set delegate within the addTextField closure like this.

class ViewController: UIViewController {

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        let alert = UIAlertController(title: "Title", message: "Message", preferredStyle: .alert)
        alert.addTextField { textField in
            textField.delegate = self
            textField.addTarget(self, action: #selector(self.textChanged(_:)), for: .editingChanged)
            textField.placeholder = "Enter name"
        }
        alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: nil))
        present(alert, animated: true, completion: nil)
    }
    @objc func textChanged(_ sender: UITextField) {
        print("Text changed - ", sender.text!)
    }
}
extension ViewController: UITextFieldDelegate {
    func textFieldDidBeginEditing(_ textField: UITextField) {
        print("EDITING")
    }
    func textFieldDidEndEditing(_ textField: UITextField) {
        print("EDITING")
    }
}

Answer 3

You can try to get a reference to it with self.textF = alert.textFields?[0]

class ViewController: UIViewController {

    var textF:UITextField!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.

        DispatchQueue.main.asyncAfter(deadline: .now() + 2) {

            //1. Create the alert controller.
            let alert = UIAlertController(title: "Some Title", message: "Enter a text", preferredStyle: .alert)
            alert.addTextField { (textField) in
                textField.text = "Some default text"
            }
             let tex = alert.addAction(UIAlertAction(title: "OK", style: .default, handler: { [weak alert] (_) in

            })) 
            // 4. Present the alert.
            self.present(alert, animated: true, completion: nil)

            self.textF =  alert.textFields?[0]

            self.textF.addTarget(self, action: #selector(self.textFieldDidChange), for: UIControl.Event.editingChanged)

        }


    }

    @objc func textFieldDidChange() {
        print(textF.text)
    }

}