第二个嵌套模型的多个t.reference值为零

我通过两个t.references访问了belongs_to owner和belongs_to car,当我通过@car.visits.create创建新访问时,owner_id始终为零。

访问.rb

class Visit < ActiveRecord::Base
#validates :notes, presence:true
belongs_to :car
belongs_to :owner
end

所有者.rb

class Owner < ActiveRecord::Base
has_many :cars
has_many :visits    
accepts_nested_attributes_for :visits
accepts_nested_attributes_for :cars
end

汽车.rb

class Car < ActiveRecord::Base
belongs_to :owner
has_many :visits
end

访问迁移

class CreateVisits < ActiveRecord::Migration
def change
create_table :visits do |t|
  t.boolean :open
  t.text :notes
  t.references :owner
  t.references :car
  t.timestamps null: false
end

end
end

如果我

 car1 = Car.create(......)
 car1.visits.create(.....)

我得到了访问的价值。owner_id=nil,但是,car_id完全填充了正确的关系。

我错过了什么? 非常感谢您的帮助。

example from my console where owner_id: nil even when its created from a @car who has already owner_id