class Car < ActiveRecord::Base has_many :bulbs has_many :foo_bulbs, -> { where(:name => 'foo') }, :class_name => "Bulb" has_many :frickinawesome_bulbs, -> { where :frickinawesome => true }, :class_name => "Bulb" has_one :bulb has_one :frickinawesome_bulb, -> { where :frickinawesome => true }, :class_name => "Bulb" has_many :tyres has_many :engines, :dependent => :destroy has_many :wheels, :as => :wheelable, :dependent => :destroy scope :incl_tyres, -> { includes(:tyres) } scope :incl_engines, -> { includes(:engines) } scope :order_using_new_style, -> { order('name asc') } end class CoolCar < Car default_scope { order('name desc') } end class FastCar < Car default_scope { order('name desc') } end