ruby-on-rails Rails has_many：through关联使用错误的外键进行查询

d8tt03nd 于 2022-12-15 发布在 Ruby

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导轨7.0.4
我有两个Rails模型，Person和Marriage，其思想是一个Person可以通过一个Marriage连接模型拥有多个妻子和丈夫，并且可以调用Person.wives和Person.husbands来获取各自的数据。
型号代码：

class Person < ApplicationRecord
    has_many :marriages
    has_many :husbands, through: :marriages, class_name: 'Person' 
    has_many :wives, through: :marriages, class_name: 'Person' 
end

class Marriage < ApplicationRecord
    belongs_to :husband, class_name: 'Person'
    belongs_to :wife, class_name: 'Person'
end

婚姻移民法：

class CreateMarriages < ActiveRecord::Migration[7.0]
  def change
    create_table :marriages do |t|
      t.references :husband, foreign_key: { to_table: :people }, index: true
      t.references :wife, foreign_key: { to_table: :people }, index: true
      t.date :marriage_date
      t.date :termination_date

      t.timestamps
    end
  end
end

已在控制台上使用此创建人员和婚姻：

husband = Person.first
wife = Person.second
Marriage.create(husband: husband, wife: wife)

但是，调用husband.wives将返回

Person Load (0.3ms)  SELECT "people".* FROM "people" INNER JOIN "marriages" ON "people"."id" = "marriages"."wife_id" WHERE "marriages"."person_id" = ?  [["person_id", 1]]                                                     
(Object doesn't support #inspect)                                  
=>

看起来查询的最后一部分，寻找marriages.person_id，是错误的，因为我期望它使用marriages.husband_id。如何使它使用正确的外键？
我尝试过向关联中添加选项，例如foreign_key: :wife_id、source: :husband和inverse_of: :wife到has_many :husbands，在has_many :wives上也是如此，但出现了相同的结果。

ruby-on-rails

来源：https://stackoverflow.com/questions/74780199/rails-has-many-through-association-uses-wrong-foreign-key-for-query

1条答案

按热度按时间

bmp9r5qi1#

实际上，您不能将一个has_many关联与 other 表中的两个不同外键一起使用，而是需要两个不同的关联：

class Person < ApplicationRecord
   has_many :marriages_as_wife, 
     class_name: 'Marriage',
     foreign_key: :wife_id,
     inverse_of: :wife
   has_many :marriages_as_husband, 
     class_name: 'Marriage',
     foreign_key: :husband_id,
     inverse_of: :husband
    
   has_many :husbands, 
     through: :marriages_as_wife, 
     class_name: 'Person' 
   has_many :wives, 
     through: :marriages_as_husband, 
     class_name: 'Person' 
end

inverse_of实际上不会以任何方式改变生成的查询，它只是用来在内存中设置引用，以避免潜在的额外数据库查询。
顺便说一句，我可能会使用一个非常不同的解决方案，使用多对多连接表，以避免做出异规范性假设：

class Person
  has_many :marriage_memberships
  has_many :marriages, 
    through: :marriage_memberships
  has_many :spouses, 
    through: :marriages,
    source: :people
end

class Marriage
  has_many :marriage_memberships
  has_many :people, through: :marriage_memberships
end 

# I can't come up with a better name
class MarriageMemberships
  belongs_to :person
  belongs_to :marriage
end

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ruby-on-rails Rails has_many：through关联使用错误的外键进行查询

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