class VC {
    @IBOutlet var buttons: [UIButton]
    @IBOUtlet var button1: UIButton!
    @IBOUtlet var button2: UIButton!
    @IBOUtlet var button3: UIButton!

    @objc func clicked(sender: UIButton) {
       //this
       if sender == buttons[0] {

       } else if sender == buttons[1] {

       }
      //or either this
       if sender == button1 {

       } else if sender == button2 {


       }
    }
}