admin_controller.rb

  def area

    # only fetch the list of areas if we have a region
    if !params[:region_id].blank?

      @region = Region.find(params[:region_id])
      @areas = @region.areas

      # save the selected region
      session[:region_id] = @region.id
    else

      @areas = Array.new
    end

    @area = Area.new
  end