simple user roles management with ActiveRecord

role_play.rb

module RolePlay
  module PluginMethods
    def has_roleplay(roles = {})
      @@roles = roles
      @@roles_ids = roles.invert

      def roles
        @@roles
      end

      def find_by_role(role_name, *args)
        find(:all, :conditions => { :role_id => @@roles[role_name]}, *args)
      end

      define_method 'role?' do |r|
        r == @@roles_ids[role_id]
      end

      define_method :role do
        @@roles_ids[role_id]
      end
    end
  end
end

ActiveRecord::Base.extend RolePlay::PluginMethods

user.rb

class User < ActiveRecord::Base
  #...
  has_roleplay(:admin => 0, :student => 1)
  #...
end