let sel = #selector(함수명)

다른 객체의 함수를 참조하는 경우

let sel = #selector(객체명.함수명) as ( 객체명 ) - > (파라미터 자료형) -> (함수반환형)

        //action sheet title 지정

        let optionMenu = UIAlertController(title: nil, message: "Choose Option", preferredStyle: .actionSheet)

        //옵션 초기화

        let deleteAction = UIAlertAction(title: "Delete", style: .default, handler: {

            (alert: UIAlertAction!) -> Void in

        })

        let saveAction = UIAlertAction(title: "Save", style: .default, handler: {

            (alert: UIAlertAction!) -> Void in

        })

        let cancelAction = UIAlertAction(title: "Cancel", style: .cancel, handler: {

            (alert: UIAlertAction!) -> Void in

      })

       //action sheet에 옵션 추가.

        optionMenu.addAction(deleteAction)

        optionMenu.addAction(saveAction)

        optionMenu.addAction(cancelAction)

       //show

        self.present(optionMenu, animated: true, completion: nil)