How do I validate TextFields in an UIAlertController?

Question

Can anyone tell me how to validate UITextFields inside of a UIAlertController?

I need it to prevent the user from clicking \"Save\" unless

Answer 1

Register for the text field change notifications and validate the text fields there:

//...
alert.addTextFieldWithConfigurationHandler {
    (textFieldEmail: UITextField!) in
    textFieldEmail.placeholder = "Enter valid email adress"
    textFieldEmail.keyboardType = .EmailAddress
}   

let textFieldValidationObserver: (NSNotification!) -> Void = { _ in
    let textFieldName = alert.textFields![0] as! UITextField
    let textFieldEmail = alert.textFields![1] as! UITextField
    saveAction.enabled = self.isValidEmail(textFieldEmail.text) && textFieldName.text.length > 0
}

// Notifications for textFieldName changes
NSNotificationCenter.defaultCenter().addObserverForName(UITextFieldTextDidChangeNotification,
    object: alert.textFields![0],  // textFieldName
    queue: NSOperationQueue.mainQueue(), usingBlock: textFieldValidationObserver)

// Notifications for textFieldEmail changes
NSNotificationCenter.defaultCenter().addObserverForName(UITextFieldTextDidChangeNotification,
    object: alert.textFields![1],  // textFieldEmail
    queue: NSOperationQueue.mainQueue(), usingBlock: textFieldValidationObserver)

alert.addAction(saveAction)
//...