forums_controller.rb

 def show
    @forum = Forum::Forum.find_by_id(params[:id])
    if @forum.hidden && !(user_in?([:admins, :masters]) || user_permitted?(:show_hidden))
      url = case @forum.parent_id
              when 0 then forum_index_path
              else forum_path(@forum.parent)
            end
      redirect_to url
    end
    rendering the forum 
  end