gistfile1.builder

module Categorizable

  def self.included(base)

    base.has_many :audience_scopes, :as => :audienciable
    base.has_many :audience_categories, :through => :audience_scopes

    base.has_many :areas, :through => :audience_scopes
    ...

    base.send :extend, ClassMethods
  end

  module ClassMethods

    def acts_as_categorizable
      send :include, InstanceMethods
    end

    def for_user(user)
      ...
    end

  end

  module InstanceMethods

    def related
      ...
    end

  end
end

ActiveRecord::Base.send :include, Categorizable