使用`assign_attributes`立即保存`has_many through:`关联

Question

据我所知，

assign_attributes

（与

update_attributes

不同）不应该保存记录或任何记录。

因此，当我发现为

_ids

关系提供

has_many through:

时，情况并非如此时，我感到非常震惊。

考虑以下示例：

class GroupUser < ApplicationRecord
  belongs_to :group
  belongs_to :user
end

class Group < ApplicationRecord
  has_many :group_users
  has_many :users, through: :group_users
end

class User < ApplicationRecord
  has_many :group_users
  has_many :groups, through: :group_users

  validates :username, presence: true
end

因此，我们的用户和组之间存在多点关系。

Group.create # Create group with ID 1
Group.create # Create group with ID 2

u = User.create(username: 'Johny')

# The following line inserts two `GroupUser` join objects, despite the fact 
# that we have called `assign_attributes` instead of `update_attributes` 
# and, equally disturbing, the user object is not even valid as we've 
# supplied an empty `username` attribute.
u.assign_attributes(username: '', group_ids: [1, 26])

评论者要求的日志：

irb(main):013:0> u.assign_attributes(username: '', group_ids: [1, 2])
  Group Load (0.2ms)  SELECT "groups".* FROM "groups" WHERE "groups"."id" IN (1, 2)
  Group Load (0.1ms)  SELECT "groups".* FROM "groups" INNER JOIN "group_users" ON "groups"."id" = "group_users"."group_id" WHERE "group_users"."user_id" = ?  [["user_id", 1]]
   (0.0ms)  begin transaction
  SQL (0.3ms)  INSERT INTO "group_users" ("group_id", "user_id", "created_at", "updated_at") VALUES (?, ?, ?, ?)  [["group_id", 1], ["user_id", 1], ["created_at", "2017-06-29 08:15:11.691941"], ["updated_at", "2017-06-29 08:15:11.691941"]]
  SQL (0.1ms)  INSERT INTO "group_users" ("group_id", "user_id", "created_at", "updated_at") VALUES (?, ?, ?, ?)  [["group_id", 2], ["user_id", 1], ["created_at", "2017-06-29 08:15:11.693984"], ["updated_at", "2017-06-29 08:15:11.693984"]]
   (2.5ms)  commit transaction
=> nil

我敢说

update_attributes

和

_ids

构造主要用于处理 Web 表单 - 在本例中是更新用户本身及其组关联的表单。所以我认为可以肯定地说，这里的一般假设是“全有或全无”，而不是部分保存。 我是否在某些方面使用错误？

Answer 1

https://github.com/rails/rails/issues/17368

阅读有关该问题的信息。其中一条评论指出了一种临时解决方法：https://gist.github.com/sudoremo/4204e399e547ff7e3afdd0d89a5aaf3e

Answer 2

  ruby: 
  def assign_parameters(attributes, options = {})
    with_transaction_returning_status {self.assign_attributes(attributes, options)}
  end

Answer 3

@item.assign_attributes{ year: "2021", type: "bad" }.valid?