# File gtk/sample/gtk-demo/list_store.rb, line 124
    def fixed_toggled(model, path_str)
      path = Gtk::TreePath.new(path_str)

      # get toggled iter
      iter = model.get_iter(path)
      fixed =iter[COLUMN_FIXED]

      # do something with the value
      fixed ^= 1

      # set new value
      iter[COLUMN_FIXED] = fixed
    end