グリッド行選択について

PHP Code:
{define-class public SwichSelectRecordgrid {inherits RecordGrid}
  field private switch-selection?:bool = false
  {constructor public {default switch-selection?:bool=false, ...}
    set self.switch-selection? = switch-selection?
    {construct-super {splice ...}}
  }

  {method public {select-record
                     index:int,
                     additive?:bool = false
                 }:void
    || new behavior
    {if self.switch-selection?  then
        {if {self.selection.contains-record? index} then
            {self.deselect-record index}
         else
            {super.select-record
                index, 
                additive? = true
            }
        }
        
     || default behavior
     else
        {super.select-record index, 
            additive? = additive?
        }
    }
    
  }
}