ruby-on-rails - rails 5 has_many through order on through table

Question

我要订购一个 has_many through直通表中某列的关系

class DoctorProfile
  has_many :doctor_specialties
  has_many :specialties, through: :doctor_specialties

class Specialty
  has_many :doctor_specialties
  has_many :doctor_profiles, through: :doctor_specialties

class DoctorSpecialty
  belongs_to :doctor_profile
  belongs_to :specialty

我想按专栏订购医生专业 ordinal在 DoctorSpecialty .特别是在使用 includes 时会发生此错误
DoctorProfile.includes(:specialties).all
我试过了
has_many :specialties, -> { order 'doctor_specialties.ordinal' }, through: :doctor_specialties

DoctorProfile Load (0.6ms)  SELECT  "doctor_profiles".* FROM "doctor_profiles" ORDER BY "doctor_profiles"."id" ASC LIMIT $1  [["LIMIT", 1]]
  DoctorSpecialty Load (0.8ms)  SELECT "doctor_specialties".* FROM "doctor_specialties" WHERE "doctor_specialties"."doctor_profile_id" = 1
  Specialty Load (0.4ms)  SELECT "specialties".* FROM "specialties" WHERE "specialties"."id" = 69 ORDER BY doctor_specialties.ordinal

并收到一个丢失的 FROM 子句错误 PG::UndefinedTable: ERROR: missing FROM-clause entry for table "doctor_specialties"
我如何定义直通表上的顺序，以便特色菜按升序返回？

注:

我能够通过添加 default_scope 来实现这一点。至 DoctorSpecialty default_scope { order('ordinal ASC') }
但是，我仍然想知道是否有办法在 has_many through 上做到这一点。

Answer 1

我能够使用它来工作

class DoctorProfile
    has_many :specialties, -> { order 'doctor_specialties.ordinal' }, through: :doctor_specialties

end

class DoctorSpecialty < ApplicationRecord
  belongs_to :doctor_profile
  belongs_to :specialty

  default_scope { order('ordinal ASC') }

end