UIAlertController in swift.

UIAlertView and UIActionSheet are Deprecated in iOS8 and Later. So Apple Introduce new controller for Alertview and ActionSheet called UIAlertController , changing the preferredStyle, you can switch alert or ActionSheet. There is no delegate in it, all button event handle in block.

NOTE : This tutorial only for Alert View, Set preferredStyle :UIAlertControllerStyle.Alert.

1. Simple :

let alertController = UIAlertController(title: "Simple", message: "Simple alertView demo with Cancel and Ok.", preferredStyle: UIAlertControllerStyle.Alert)
let cancelAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.Cancel) { (result : UIAlertAction) -> Void in
            print("Cancel")
        }
let okAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.Default) { (result : UIAlertAction) -> Void in
            print("OK")
        }
alertController.addAction(cancelAction)
alertController.addAction(okAction)
self.presentViewController(alertController, animated: true, completion: nil)

2. Destructive :

let alertController = UIAlertController(title: "Destructive", message: "Simple alertView demo with Destructive and Ok.", preferredStyle: UIAlertControllerStyle.Alert)
let DestructiveAction = UIAlertAction(title: "Destructive", style: UIAlertActionStyle.Destructive) { (result : UIAlertAction) -> Void in
            print("Destructive")
        }
let okAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.Default) { (result : UIAlertAction) -> Void in
            print("OK")
        }
alertController.addAction(DestructiveAction)
alertController.addAction(okAction)
self.presentViewController(alertController, animated: true, completion: nil)

3. PlainTextStyle :

let alertController = UIAlertController(title: "PlainTextStyle", message: "PlainTextStyle AlertView.", preferredStyle: UIAlertControllerStyle.Alert)
alertController.addTextFieldWithConfigurationHandler { (textField : UITextField) -> Void in
            textField.placeholder = "Login"
        }
let cancelAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.Cancel) { (result : UIAlertAction) -> Void in
            print("Cancel")
        }
let okAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.Default) { (result : UIAlertAction) -> Void in
           print(alertController.textFields?.first?.text)
        }
alertController.addAction(cancelAction)
alertController.addAction(okAction)
self.presentViewController(alertController, animated: true, completion: nil)

4. SecureStyle :

let alertController = UIAlertController(title: "SecureStyle", message: "SecureStyle AlertView.", preferredStyle: UIAlertControllerStyle.Alert)
alertController.addTextFieldWithConfigurationHandler { (textField : UITextField) -> Void in
            textField.secureTextEntry = true
            textField.placeholder = "Password"
        }
let cancelAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.Cancel) { (result : UIAlertAction) -> Void in
            print("Cancel")
        }
let okAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.Default) { (result : UIAlertAction) -> Void in
            print(alertController.textFields?.first?.text)
        }
alertController.addAction(cancelAction)
alertController.addAction(okAction)
self.presentViewController(alertController, animated: true, completion: nil)

5. LoginStyle:

let alertController = UIAlertController(title: "LoginStyle", message: "LoginStyle AlertView.", preferredStyle: UIAlertControllerStyle.Alert)
alertController.addTextFieldWithConfigurationHandler { (textField : UITextField) -> Void in
            textField.placeholder = "Login"
            textField.addTarget(self, action: "alertTextFieldDidChange:", forControlEvents: UIControlEvents.EditingChanged)
        }
alertController.addTextFieldWithConfigurationHandler { (textField : UITextField) -> Void in
            textField.secureTextEntry = true
            textField.placeholder = "Password"
        }
let cancelAction = UIAlertAction(title: "Cancel", style: UIAlertActionStyle.Cancel) { (result : UIAlertAction) -> Void in
            print("Cancel")
        }
let okAction = UIAlertAction(title: "OK", style: UIAlertActionStyle.Default) { (result : UIAlertAction) -> Void in
            print(alertController.textFields?.first?.text)
        }
okAction.enabled = false
alertController.addAction(cancelAction)
alertController.addAction(okAction)
self.presentViewController(alertController, animated: true, completion: nil)

function to check textfield text condition.

func alertTextFieldDidChange(sender : UITextField){
      let alertV = self.presentedViewController as? UIAlertController
      let login = (alertV!.textFields?.first)! as UITextField
      let okAction = alertV!.actions.last! as UIAlertAction
      okAction.enabled = login.text?.characters.count > 2
   }