ruby-on-rails - 多重自​​引用 has_many :through associations in Rails 4.

Question

我正在编写一些使用多个自引用模型的代码，我希望能够使用连接表进行匹配，因为它们是通过连接表关联的。

模型看起来像

用户.rb:

class User < ActiveRecord::Base
  has_many :appointments
  has_many :students, through: :appointments
  has_many :teachers, through: :appointments
end

约会.rb:

class Appointment < ActiveRecord::Base
  belongs_to :student, class_name: User
  belongs_to :teacher, class_name: User
end

不幸的是，Rails 生成的查询是:

SELECT "users".* FROM "users" INNER JOIN "appointments" ON "users"."id" = "appointments"."student_id" WHERE "appointments"."user_id" = $1

这会引发错误，因为 Appointment 没有 user_id 参数。

我已经尝试指定 foreign_key 选项，但这没有任何作用。还有其他方法可以优雅地解决这个问题吗？

非常感谢。

Answer 1

我已经设法解决了。 has_many :through 所基于的 has_many 必须设置 foreign_key 选项。代码变成了:

class User < ActiveRecord::Base
  has_many :appointments_as_student, foreign_key: :student_id, class_name: Appointment
  has_many :appointments_as_teacher, foreign_key: :teacher_id, class_name: Appointment

  has_many :students, through: :appointments_as_teacher
  has_many :teachers, through: :appointments_as_student
end

感谢大家的努力。