From the UIAlertView class:

// UIAlertView is deprecated. Use UIAlertController with apreferredStyle of UIAlertControllerStyleAlert instead

On iOS 8, you can do this:

let alert = UIAlertController(title: "Alert", message: "Message", preferredStyle: UIAlertControllerStyle.Alert)alert.addAction(UIAlertAction(title: "Click", style: UIAlertActionStyle.Default, handler: nil))self.presentViewController(alert, animated: true, completion: nil)

Now UIAlertController is a single class for creating and interacting with what we knew as UIAlertViews and UIActionSheets on iOS 8.

Edit: To handle actions:

alert.addAction(UIAlertAction(title: "OK", style: .Default, handler: { action in    switch action.style{    case .Default:        print("default")            case .Cancel:        print("cancel")            case .Destructive:        print("destructive")    }}}))

Edit for Swift 3:

let alert = UIAlertController(title: "Alert", message: "Message", preferredStyle: UIAlertControllerStyle.alert)alert.addAction(UIAlertAction(title: "Click", style: UIAlertActionStyle.default, handler: nil))self.present(alert, animated: true, completion: nil)

Edit for Swift 4.x:

let alert = UIAlertController(title: "Alert", message: "Message", preferredStyle: .alert)alert.addAction(UIAlertAction(title: "OK", style: .default, handler: { action in    switch action.style{        case .default:        print("default")                case .cancel:        print("cancel")                case .destructive:        print("destructive")            }}))self.present(alert, animated: true, completion: nil)

One Button

class ViewController: UIViewController {    @IBAction func showAlertButtonTapped(_ sender: UIButton) {        // create the alert        let alert = UIAlertController(title: "My Title", message: "This is my message.", preferredStyle: UIAlertController.Style.alert)        // add an action (button)        alert.addAction(UIAlertAction(title: "OK", style: UIAlertAction.Style.default, handler: nil))        // show the alert        self.present(alert, animated: true, completion: nil)    }}

Two Buttons

class ViewController: UIViewController {    @IBAction func showAlertButtonTapped(_ sender: UIButton) {        // create the alert        let alert = UIAlertController(title: "UIAlertController", message: "Would you like to continue learning how to use iOS alerts?", preferredStyle: UIAlertController.Style.alert)        // add the actions (buttons)        alert.addAction(UIAlertAction(title: "Continue", style: UIAlertAction.Style.default, handler: nil))        alert.addAction(UIAlertAction(title: "Cancel", style: UIAlertAction.Style.cancel, handler: nil))        // show the alert        self.present(alert, animated: true, completion: nil)    }}

Three Buttons

class ViewController: UIViewController {    @IBAction func showAlertButtonTapped(_ sender: UIButton) {        // create the alert        let alert = UIAlertController(title: "Notice", message: "Lauching this missile will destroy the entire universe. Is this what you intended to do?", preferredStyle: UIAlertController.Style.alert)        // add the actions (buttons)        alert.addAction(UIAlertAction(title: "Remind Me Tomorrow", style: UIAlertAction.Style.default, handler: nil))        alert.addAction(UIAlertAction(title: "Cancel", style: UIAlertAction.Style.cancel, handler: nil))        alert.addAction(UIAlertAction(title: "Launch the Missile", style: UIAlertAction.Style.destructive, handler: nil))        // show the alert        self.present(alert, animated: true, completion: nil)    }}

Handling Button Taps

The handler was nil in the above examples. You can replace nil with a closure to do something when the user taps a button. For example:

alert.addAction(UIAlertAction(title: "Launch the Missile", style: UIAlertAction.Style.destructive, handler: { action in    // do something like...    self.launchMissile()}))

Notes

• Multiple buttons do not necessarily need to use different UIAlertAction.Style types. They could all be .default.
• For more than three buttons consider using an Action Sheet. The setup is very similar. Here is an example.

You can create a UIAlert using the standard constructor, but the 'legacy' one seems to not work:

let alert = UIAlertView()alert.title = "Alert"alert.message = "Here's a message"alert.addButtonWithTitle("Understood")alert.show()