self.showAlertWithButtonClicked(clickedButton: { (clickedButton) -> Void in
        //check the button index by clickedButton.tag

        })

class MyAlertController: UIViewController {


typealias CompletionHandler = (_ clickedButton: UIButton) -> Void
override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.
}

func showAlertWithButtonClicked(clickedButton: @escaping (MultipleMethodRunningHandle)) {
    //Do what you want

}

func pressedCancelButton(button: UIButton) {
    //At this point compiler doesn't allow me to use that completionHandler globally in the class
    button.tag = 0
    clickedButton(button)
}
func pressedSendButton(button: UIButton) {
    //At this point compiler doesn't allow me to use that completionHandler globally in the class
    button.tag = 1
    clickedButton(button)
}
func pressedAddButton(button: UIButton) {
    //At this point compiler doesn't allow me to use that completionHandler globally in the class
    button.tag = 2
    clickedButton(button)
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}