Polymorphic association example with "belong_to".

gistfile1.rb

class Vehicle < ActiveRecord::Base
  validates :name, presence: true
end

class Car < ActiveRecord::Base
  belongs_to :vehicle
  accepts_nested_attributes_for :vehicle
  delegate :name, to: :vehicle
end

--

> c = Car.new(doors: 4, vehicle_attributes: { name: 'Golf', brand: 'Volkswagen' })
> c.name #=> "Golf"