Controller before_filter

answer #4

   class HomeController < ApplicationController
#    use code block as filter
     before_filter do |controller|
         controller.send(:intruder?)   # call intruder? method in the controller
#         ...
     end

     def intruder?
#       ...
     end
   end

#  another example:
   class WeblogController < ActionController::Base
       before_filter { |controller| head(400) if controller.params["stop_action"] }
   end