Return text from UIAlertController into an extension - ios

Question

In Swift, how can I return the string that I write into the UIAlertController's textfield, added if this UIAlertController is inside an extension
Usually if you put your UIAlertController implementation locally in your class, you can easily pass the text, but when the alert is into an extension, I'm not sure which could be the way to return the text.
For example, assume you have this extension:
extension UIViewController {
func presentTextFieldAlert(title: String, message: String, textFieldPlaceholder: String ) {
let alertController = UIAlertController(title: title, message: message, preferredStyle: .alert)
let saveAction = UIAlertAction(title: "OK", style: UIAlertAction.Style.default) { _ -> Void in
let urlTextField = alertController.textFields![0] as UITextField
if urlTextField.text != nil { }
}
let cancelAction = UIAlertAction(title: "Cancel", style: .default)
alertController.addTextField { (textField: UITextField!) -> Void in
textField.placeholder = textFieldPlaceholder
}
alertController.addAction(saveAction)
alertController.addAction(cancelAction)
self.present(alertController, animated: true, completion: nil)
}
}
and into your class:
class Client: UIViewController {
func showAlert() {
self.presentTextFieldAlert(title: "Hello", message: "Write sth", textFieldPlaceholder: "Write here")
}
}
how can I pass the text from the alert to the viewcontroller?
I've tried something like:
class Client: UIViewController {
func showAlert() -> String {
return self.presentTextFieldAlert(title: "Hello", message: "Write sth", textFieldPlaceholder: "Write here")
}
}
but I think it is not the correct way.

Answer 1

Use a completion handler.
extension UIViewController {
func presentTextFieldAlert(title: String, message: String, textFieldPlaceholder: String, completion: #escaping (String?)->()) {
let alertController = UIAlertController(title: title, message: message, preferredStyle: .alert)
let saveAction = UIAlertAction(title: "OK", style: UIAlertAction.Style.default) { _ -> Void in
let urlTextField = alertController.textFields![0] as UITextField
completion(urlTextField.text)
}
let cancelAction = UIAlertAction(title: "Cancel", style: .default)
alertController.addTextField { (textField: UITextField!) -> Void in
textField.placeholder = textFieldPlaceholder
completion(nil)
}
alertController.addAction(saveAction)
alertController.addAction(cancelAction)
self.present(alertController, animated: true, completion: nil)
}
}
Then you can use it as:
class Client: UIViewController {
func showAlert() {
self.presentTextFieldAlert(title: "Hello", message: "Write sth", textFieldPlaceholder: "Write here") { (result) in
if let result = result {
// User entered some text and tapped OK.
}
}
}
}