Rails 多态连接 has_many，通过 returns 不可能 SQL

Question

我有3个模型设置如下：

class User < ActiveRecord::Base

  has_many :interests, as: :interesting, dependent: :destroy
  has_many :games, through: :interests, source: :interesting, source_type: 'Game'
  has_many :people, through: :interests, source: :interesting, source_type: 'Person'

end

class Interest < ActiveRecord::Base

  belongs_to :interesting, polymorphic: true
  validates :user_id, presence: true
  validates :interesting_id, presence: true
end

class Game < ActiveRecord::Base
   has_many :users, through: :interests
   has_many :interests, as: :interesting
end

class Person < ActiveRecord::Base

  has_many :users, through: :interests
  has_many :interests, as: :interesting

end

当我尝试调用 user.games 时，数据库中的 SQL 运行是

SELECT "games".* FROM "games" 
INNER JOIN "interests" 
ON "game"."id" = "interests"."interesting_id" 
WHERE "interests"."interesting_id" =  AND
    "interests"."interesting_type" =  AND
    "interests"."interesting_type" =   
[["interesting_id", 3], 
["interesting_type", "User"], 
["interesting_type", "Game"]]

所以显然没有返回任何内容。只要不包含 ["interesting_type", "User"]，查询就应该有效。

我做错了什么？设置 User class 以及 Game 和 Person class 的最佳方法是什么？

我正在使用 Rails v4.2.6

Answer 1

请试试这个

class User < ActiveRecord::Base

  has_many :interests, dependent: :destroy
  has_many :games, as: :interesting, through: :interests, source_type: 'Game'
  has_many :people, as: :interesting, through: :interests, source_type: 'Person'

end

class Interest < ActiveRecord::Base

  belongs_to :interesting, polymorphic: true
  validates :user_id, presence: true # I don't know the reason to use that if you use as polymorphic 
  validates :interesting_id, presence: true 
end

table_name interests 它应该只有属性 :id:, :interesting_id, :interesting_type

Answer 2

总而言之，以下似乎适用于此用例：

User < ActiveRecord::Base 
  has_many :interests, dependent: :destroy 
  has_many :games, through: :interests, 
           source: :interesting, source_type: 'Game'
  has_many :people, through: :interests, 
           source: :interesting, source_type: 'Person'

end

class Interest < ActiveRecord::Base
  belongs_to :user
  belongs_to :interesting, polymorphic: true
  validates :user_id, presence: true 
  validates :interesting_id, presence: true 
end

Rails 多态连接 has_many，通过 returns 不可能 SQL

Rails polymorphic join has_many, through returns impossible SQL

ruby-on-rails

polymorphic-associations