用户表中的数据示例

rails控制台中的预期结果， grandfather.grandchildren 及 grandmother.grandchildren 应返回相同的对象组：

grandfather = User.first
grandfather.grandchildren
=> #<ActiveRecord::Associations::CollectionProxy [#<User id: 5, name: "father's son", father_id: 3, mother_id: nil>, #<User id: 6, name: "uncle's son", father_id: 4, mother_id: nil>]>
grandmother = User.find(2)
grandmother.grandchildren
=> #<ActiveRecord::Associations::CollectionProxy [#<User id: 5, name: "father's son", father_id: 3, mother_id: nil>, #<User id: 6, name: "uncle's son", father_id: 4, mother_id: nil>]>

这是我现在在user.rb模型中的关联。

has_many :children, ->(user) { unscope(:where).where("father_id = :id OR mother_id = :id", id: user.id) }, class_name: "User"
 has_many :grandchildren, through: :children, source: :children
 belongs_to :mother, class_name: "User", optional: true
 belongs_to :father, class_name: "User", optional: true

现在在rails控制台中输出：

irb(main):001:0> grandfather = User.first
   (0.3ms)  SELECT sqlite_version(*)
  User Load (0.2ms)  SELECT "users".* FROM "users" ORDER BY "users"."id" ASC LIMIT ?  [["LIMIT", 1]]
=> #<User id: 1, name: "grandfather", mother_id: nil, father_id: nil>
irb(main):002:0> grandfather.grandchildren
  User Load (0.3ms)  SELECT "users".* FROM "users" INNER JOIN "users" "children_grandchildren" ON "users"."user_id" = "children_grandchildren"."id" WHERE (father_id = 1 OR mother_id = 1) /* loading for inspect */ LIMIT ?  [["LIMIT", 11]]
Traceback (most recent call last):
ActiveRecord::StatementInvalid (SQLite3::SQLException: ambiguous column name: father_id)