Before Filter

before_filter.rb

class A
  def self.before_filters
    @before_filters ||= []
  end

  def self.before_filter(callback, params={})
    before_filters << params.merge(:callback => callback)
  end

  def self.inherited(child_class)
    before_filters.each { |f| child_class.before_filters.unshift(f) }
  end

  def execute(action)
    matched_filters = self.class.before_filters.select do |f| 
      f[:only].nil? || f[:only].include?(action) 
    end

    matched_filters.each { |f| send f[:callback] }
    send(action)
  end
end