不能写未知属性`appointment_id'

Question

在Rails 4中，我有一个像这样的has_many关系：

class Company::Appointment < ActiveRecord::Base
  has_many :company_appointment_extras, class_name: "Company::Appointment::Extra"
  accepts_nested_attributes_for :company_appointment_extras
end

class Company::Appointment::Extra < ActiveRecord::Base
  belongs_to :company_appointment, class_name: "Company::Appointment"
end

用户使用嵌套表单同时创建这些对象。一切正常，直到写入数据库，此时我收到此错误：

can't write unknown attribute `appointment_id'

起初我认为错误是从Company::Appointment::Extra引发的，但当我尝试将foreign_key: "company_appointment_id"添加到belongs_to减速时，我继续得到unknown attribute 'appointment_id'错误，这意味着错误不是来自那种关系。

事实上，在控制台中查看，在编写Company::Appointment本身时，似乎确实发生了错误：

SQL (1.0ms)  INSERT INTO "company_appointments" ("company_id", "created_at", "date", "total", "updated_at", "user_property_id") VALUES ($1, $2, $3, $4, $5, $6) RETURNING "id"  [["company_id", 1], ["created_at", Thu, 05 Sep 2013 04:58:19 UTC +00:00], ["date", Fri, 06 Sep 2013 00:00:00 UTC +00:00], ["total", #<BigDecimal:6ac2118,'0.55E2',9(27)>], ["updated_at", Thu, 05 Sep 2013 04:58:19 UTC +00:00], ["user_property_id", 1]]
(0.3ms)  ROLLBACK
Completed 500 Internal Server Error in 452ms

知道为什么会这样吗？

编辑：

我应该澄清一下，在我的迁移中，我宣布：t.integer :company_appointment_id, null: false。密钥实际上是company_appointment_id，而不是appointment_id。