module Filter
  module ClassMethods
    def before_filter(sym, *only)
      only.each do |method|
        module_eval <<-END
          def #{method}_with_before_filter(*args, &block)
            send :#{sym}
            send :#{method}_without_before_filter, *args, &block
          end
          alias_method :"#{method}_without_before_filter", :#{method}
          alias_method :#{method}, :"#{method}_with_before_filter"
        END
      end
    end
  end

  def self.included(mod)
    mod.send :extend, ClassMethods
  end
end