button function

ViewController.swift

@IBAction func showMessage(sender: UIButton) {
  var enabled = false      
  
  let alertController = UIAlertController(title: "Alert", message: enabled ? "Hello World!" : "Nothing to see here...", preferredStyle: UIAlertController.Style.alert)
  
  if enabled {
      alertController.addAction(UIAlertAction(title: "Hello!", style: UIAlertAction.Style.default, handler: nil))
  } else {
      alertController.addAction(UIAlertAction(title: "Ok", style: UIAlertAction.Style.default, handler: nil))
  }

  present(alertController, animated: true, completion: nil)
}