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Abstract

BAction func showAlertButtonTapped( sender: UIButton) {</pre></div><div id="53c6"><pre> // create the alert let alert = UIAlertController(title: "UIAlertController", message: "Would you like to continue learning how to use iOS alerts?", preferredStyle: UIAlertController.Style.alert)</pre></div><div id="71b7"><pre> // 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))</pre></div><div id="1c50"><pre> // show the alert self.present(alert, animated: true, completion: nil) } }</pre></div><h1 id="729b">Three Buttons</h1><figure id="455f"><img src="https://cdn-images-1.readmedium.com/v2/resize:fit:800/0*_bhMp2CzeLLKPDdO.png"><figcaption></figcaption></figure><div id="b218"><pre>class ViewController: UIViewController {</pre></div><div id="9ccd"><pre> @IBAction func showAlertButtonTapped( sender: UIButton) {</pre></div><div id="4870"><pre> // create the alert let alert = UIAlertController(title: "Notice", message: "Lauching this missile will destroy the entire universe. Is this what you intended to do?",

Options

preferredStyle: UIAlertController.Style.alert)</pre></div><div id="001e"><pre> // add the actions (buttons) alert.addAction(UIAlertAction(title: "Remind Me Tomorrow", style: UIAlertAction.Style.default, handler: nil)) alert.addAction(UIAlertAction(title: "Cancel", style: UIAlertActio.nStyle.cancel, handler: nil)) alert.addAction(UIAlertAction(title: "Launch the Missile", style: UIAlertAction.Style.destructive, handler: nil))</pre></div><div id="e086"><pre> // show the alert self.present(alert, animated: true, completion: nil) } }</pre></div><h1 id="116e">Handling Button Taps</h1>The <code>handler</code> was <code>nil</code> in the above examples. You can replace <code>nil</code> with a <a href="https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Closures.html">closure</a> to do something when the user taps a button. For example:<div id="5425"><pre>alert.addAction(UIAlertAction(title: "Launch the Missile", style: UIAlertAction.Style.destructive, handler: { action in</pre></div><div id="defe"><pre> // do something like... self.launchMissile()</pre></div><div id="f0b3"><pre>}))</pre></div><h1 id="a1f8">Notes</h1><ul><li>Multiple buttons do not necessarily need to use different <code>UIAlertAction.Style</code> types. They could all be <code>.default</code>.</li><li>For more than three buttons consider using an Action Sheet. The setup is very similar. <a href="https://stackoverflow.com/a/32991999/3681880">Here is an example.</a></li></ul></article></body>

Making an Alert in iOS

This is a repost of an answer I wrote on Stack Overflow.

Alerts are useful for displaying a message to a user and optionally giving them a chance to respond to it. In iOS you us a UIAlertController to do that. This is the equivalent of an Android AlertDialog (or a Flutter AlertDialog). The examples below show a basic setup for one, two, and three buttons.

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: UIAlertActio.nStyle.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.