How To Produce Checkbox Outcome Inward Swift

A really uncomplicated checkbox control.

 @IBAction func btn_box(sender: UIButton) {

        if (btn_box.selected == true)

        {

            btn_box.setBackgroundImage(UIImage(named: "box"), forState: UIControlState.Normal)

            

                btn_box.selected = false;

        }

        else

        {

            btn_box.setBackgroundImage(UIImage(named: "checkBox"), forState: UIControlState.Normal)

            

            btn_box.selected = true;

        }

    }