Rails：has_many通過多個外鍵？

Question

我有2個表和一個連接表：

型號1：

class Book < ActiveRecord::Base
  has_many :book_people
  has_many :illustrators, through: :book_people, class_name: 'ComaPerson', foreign_key: 'illustrator_id'
  has_many :authors, through: :book_people, class_name: 'ComaPerson', foreign_key: 'author_id'

加入表：

class BookPerson < ActiveRecord::Base
  belongs_to :book
  belongs_to :illustrator, class_name: 'ComaPerson', foreign_key: 'illustrator_id'
  belongs_to :author, class_name: 'ComaPerson', foreign_key: 'author_id'

模型2（給我問題的那個）：

class ComaPerson < ActiveRecord::Base
  has_many :book_people #<-- not working
  has_many :books, :through => :book_people

我的測試失敗了，因為它說BookPerson模型沒有coma_person_id列：

Failures:

  1) ComaPerson should have many book_people
     Failure/Error: it { should have_many(:book_people) }
       Expected ComaPerson to have a has_many association called book_people (BookPerson does not have a coma_person_id foreign key.)
     # ./spec/models/coma_person_spec.rb:5:in `block (2 levels) in <top (required)>'

由於ComaPerson可以是插圖畫家或作者，我在連接表中使用了illustrator_id和author_id ，因此連接表有三列'book_id，illustrator_id和author_id'。 這是否意味着我必須在連接表中添加coma_person_id列才能使其工作？

Answer 1

我想我明白了。 因此，您必須屏蔽has_many :join_table_name並將它們拆分為兩個，每個foreign_key一個，同時指定模型名稱和外鍵。

class ComaPerson < ActiveRecord::Base
  has_many :authored_books_people, class_name: 'BookPerson', foreign_key: 'author_id'
  has_many :illustrated_book_people, class_name: 'BookPerson', foreign_key: 'illustrator_id'
  has_many :authored_books, through: :authored_books_people, primary_key: 'author_id', source: :book
  has_many :illustrated_books, through: :illustrated_book_people, primary_key: 'illustrator_id', source: :book