ClassRegistry

module ClassRegistry
  module ClassMethods
    def registry
      @registry ||= {}
    end

    def register(role_name, klass=self)
      registry[role_name] = klass
    end

    def registry_key
      matches = registry.select{ |key, val| val = self.class}.keys
    end

    def users
      User.where(:role_name => registry_key)
    end
  end

  def self.included(base)
    base.extend(ClassMethods)
  end
end

consumer.rb

class Role::Consumer < Role
  Role.register 'Consumer', self
end

role.rb

require 'class_registry'
class Role
  include ClassRegistry

  def self.for(user)
    registry[user.role_name].new.tap do |role|
      role.user = user
    end
  end


  def role_name
    user.role_name
  end

  attr_accessor :user

  Dir[File.dirname(__FILE__) + '/role/*.rb'].each { |file| require file }
end