Question

据我所知，assign_attributes（与update_attributes不同）不应该保存记录或任何记录。

当我为_ids关系提供has_many through:时发现这不是真的时，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，我们将用户和群组建立在m-to-m关系中。

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 - 在这种情况下是一个更新用户自身及其组关联的表单。所以我认为可以很安全地说这里的一般假设是全部或全部，而不是部分保存。

我是否以某种方式使用它？

Answer 1

@ gokul-m建议在https://github.com/rails/rails/issues/17368阅读有关此问题的信息。那里的评论之一指出了一种临时解决方法：https://gist.github.com/remofritzsche/4204e399e547ff7e3afdd0d89a5aaf3e

Answer 2

我解决此问题的示例：

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

Answer 3

您可以像这样使用assign_attributes处理验证

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

使用`assign_attributes`可以立即保存`has_many：`关联

3 个答案: