Rails ActiveRecord：保存嵌套模型回滚 [英] Rails ActiveRecord: Saving nested models is rolled back

问题描述

使用Rails 5：

gem 'rails', '~> 5.0.0', '>= 5.0.0.1'

我创建了最简单的示例可以想到来证明这个问题：

I've created the simplest example I can think of to demonstrate the issue:

parent.rb

class Parent < ApplicationRecord
  has_many :children
  accepts_nested_attributes_for :children
end

child.rb

class Child < ApplicationRecord
  belongs_to :parent
end

创建父级，保存，创建孩子，保存（工作）

使用 rails控制台，创建一个新的父对象，然后保存，然后从父母那里生一个孩子，然后保存父母，就可以了：

Using rails console, creating a new parent, then saving, then building a child from the parent, then saving the parent, works fine:

irb(main):004:0> parent = Parent.new
=> #<Parent id: nil, created_at: nil, updated_at: nil>
irb(main):005:0> parent.save
   (0.5ms)  BEGIN
  SQL (0.4ms)  INSERT INTO `parents` (`created_at`, `updated_at`) VALUES ('2016-09-25 13:05:44', '2016-09-25 13:05:44')
   (3.2ms)  COMMIT
=> true
irb(main):006:0> parent.children.build
=> #<Child id: nil, parent_id: 1, created_at: nil, updated_at: nil>
irb(main):007:0> parent.save
   (0.5ms)  BEGIN
  Parent Load (0.5ms)  SELECT  `parents`.* FROM `parents` WHERE `parents`.`id` = 1 LIMIT 1
  SQL (0.7ms)  INSERT INTO `children` (`parent_id`, `created_at`, `updated_at`) VALUES (1, '2016-09-25 13:05:52', '2016-09-25 13:05:52')
   (1.3ms)  COMMIT
=> true

创建父母，创建孩子，保存（无效）

但是，如果我尝试创建新的父级，则在不保存父级的情况下构建子级 ，最后将父级保存起来，则交易失败并回滚：

However, if I try to create a new parent, then build the child without saving the parent, and finally save the parent at the end, the transaction fails and is rolled back:

irb(main):008:0> parent = Parent.new
=> #<Parent id: nil, created_at: nil, updated_at: nil>
irb(main):009:0> parent.children.build
=> #<Child id: nil, parent_id: nil, created_at: nil, updated_at: nil>
irb(main):010:0> parent.save
   (0.5ms)  BEGIN
   (0.4ms)  ROLLBACK
=> false

有人可以解释原因以及如何解决吗？

Can anyone explain why, and how to fix?

更新

同时创建父母和子女，然后通过 validate进行保存是可行的：false ，所以这表明问题是对子项的验证失败，因为它需要设置parent_id-但是大概子项验证必须在保存父项之前那么，还是不会失败？

Creating both parent and child, then saving does work if you pass validate: false, so this points to the issue being validation of the child failing, because it requires the parent_id to be set - but presumably the child validation must be running before the parent is saved then, or it wouldn't fail?

irb(main):001:0> parent = Parent.new
=> #<Parent id: nil, created_at: nil, updated_at: nil>
irb(main):002:0> parent.children.build
=> #<Child id: nil, parent_id: nil, created_at: nil, updated_at: nil>
irb(main):003:0> parent.save(validate: false)
   (0.7ms)  BEGIN
  SQL (0.9ms)  INSERT INTO `parents` (`created_at`, `updated_at`) VALUES ('2016-09-25 15:02:20', '2016-09-25 15:02:20')
  SQL (0.8ms)  INSERT INTO `children` (`parent_id`, `created_at`, `updated_at`) VALUES (3, '2016-09-25 15:02:20', '2016-09-25 15:02:20')
   (1.6ms)  COMMIT
=> true

更新2

如果我删除了<$ c $，它也可以使用保存（没有验证：false ）工作。 child.rb 中的c> belongs_to：parent 行，因为此后没有验证 parent_id 在被保留之前是有效的-但是，您将失去从孩子那里找父母的能力（通过 child.parent ）。您仍然可以从父母那里找到孩子（通过 parent.child ）。

It also works using save (without the validation: false) if I remove the belongs_to :parent line from child.rb, since then no validation takes place that parent_id is valid before being persisted - however, then you lose ability to get at the parent from the child (via child.parent). You can still get to the child from the parent (via parent.child).

推荐答案

尝试以下操作：

class Child < ApplicationRecord
  belongs_to :parent, optional: true
end

经过一些研究我发现Rails 5现在要求在子级默认情况下中存在关联的ID。否则，Rails会触发验证错误。

After doing some research I discovered that Rails 5 now requires an associated id to be present in the child by default. Otherwise Rails triggers a validation error.

查看此文章进行了很好的解释，并提出了相关的拉出请求

Check out this article for a great explanation and the relevant pull request

...以及官方的Rails 指南对其进行非常简短的提及：

...and the official Rails guide make a very brief mention of it:

4.1.2.11：optional

4.1.2.11 :optional

如果将：optional选项设置为true，则
关联对象的存在将'待验证。默认情况下，此选项将
设置为false。

If you set the :optional option to true, then the presence of the associated object won't be validated. By default, this option is set to false.

因此您可以通过添加<$ c来关闭此新行为$ c>可选： belongs_to 对象之后的true 。

So you can turn off this new behavior by adding optional: true after the belongs_to object.

所以在您的示例中您必须先创建/保存父级，然后再生成子级，或使用可选：true

So in your example you would have to create/save Parent first before building the child, or use optional: true

这篇关于Rails ActiveRecord：保存嵌套模型回滚的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！