How to Make Hello World App Xcode (8 Swift 3.0)

function for Hello World Button

@IBAction func showMessage() {
        let alertController = UIAlertController(title: "Welcome to My First App",
                                                message: "Hello World", preferredStyle: UIAlertControllerStyle.alert)
        alertController.addAction(UIAlertAction(title: "OK", style:
            UIAlertActionStyle.default, handler: nil))
        present(alertController, animated: true, completion: nil)
    }