Ruby on Rails:依赖对象在从来宾用户转移到注册用户时销毁

Question

我的问题是:

我正在使用设计的guest_user，它包含一个logging_in方法，用于在登录时将guest_user参数传递给注册用户。在我的例子中，用户是has_many periods, dependent: :destroy，这里是logging_in方法

def logging_in
  guest_periods = guest_user.periods.all
  guest_periods.each do |p|
    p.user_id = current_user.id
    p.save!
  end
  current_user.latest_entry = guest_user.latest_entry
  current_user.is_in_zone = guest_user.is_in_zone
  current_user.save
end

然而，当一个guest_user登录时，他的周期被销毁而不是被转移。日志如下:

Started GET "/" for ::1 at 2015-05-11 00:18:03 +0300
Processing by WelcomeController#index as HTML
  User Load (0.4ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1  ORDER BY "users"."id" ASC LIMIT 1  [["id", 24]]
  User Load (0.4ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1  [["id", 23]]
  Period Load (0.3ms)  SELECT "periods".* FROM "periods" WHERE "periods"."user_id" = $1  [["user_id", 23]]
   (0.2ms)  BEGIN
  CACHE (0.0ms)  SELECT "periods".* FROM "periods" WHERE "periods"."user_id" = $1  [["user_id", 23]]
  SQL (0.8ms)  UPDATE "periods" SET "user_id" = $1, "updated_at" = $2 WHERE "periods"."id" = $3  [["user_id", 24], ["updated_at", "2015-05-10 21:18:03.863162"], ["id", 170]]
   (0.9ms)  COMMIT
   (0.2ms)  BEGIN
  SQL (2.1ms)  UPDATE "users" SET "is_in_zone" = $1, "latest_entry" = $2, "updated_at" = $3 WHERE "users"."id" = $4  [["is_in_zone", "t"], ["latest_entry", "2015-05-04"], ["updated_at", "2015-05-10 21:18:03.875572"], ["id", 24]]
   (15.8ms)  COMMIT
   (0.5ms)  BEGIN
  SQL (0.3ms)  DELETE FROM "periods" WHERE "periods"."id" = $1  [["id", 170]]
  SQL (0.7ms)  DELETE FROM "users" WHERE "users"."id" = $1  [["id", 23]]
   (1.2ms)  COMMIT

所以我们可以看到传输完成了，但最后，周期还是被破坏了。它们不应该是，因为它们不再属于要销毁的用户。

为什么会这样?

Answer 1

即使Period#user_id已经更改，guest_user.periods仍然加载在内存中，并且在您删除来宾用户时被销毁。如果你使用guest_user.reload，它的关联就会清除，破坏它就变得安全了。您还可以使用guest_user.periods(true)强制重新加载周期。

另一个选项是:

guest_user.periods.update_all(user_id: current_user.id)

这将执行单个查询来执行更新，如果有很多周期，这将是很好的，也不加载guest_user.periods关联，所以它将在销毁期间加载新鲜并找到正确的空集。