Rails 5 has_many通过表的顺序

Question

我想has_many through在通过表中的列上订购关系

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

我想医生专业被列进行排序ordinal的DoctorSpecialty。具体来说，使用时会发生此错误includes

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

并收到缺少的FROM -clause错误 PG::UndefinedTable: ERROR: missing FROM-clause entry for table "doctor_specialties"

我如何在通过表上定义顺序，以便专业按升序返回？

注意：

我可以通过添加一个default_scope来使此工作DoctorSpecialty

default_scope { order('ordinal ASC') }

但是，我仍然想知道是否有办法在 has_many through

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