Access Active Record Object Attributes in Rails Model

I have a model with the following associations:

class Car < ActiveRecord::Base
 开发者_开发技巧 belongs_to :transportation_vehicle
  belongs_to :owner
  has_many :parts

  def scrap(buyer, part)
  ...
  end
end

How would I access owner and parts in the scrap method?

owner or self.owner.