何时使用“validates_related"v"验证=>真" [英] When to use "validates_associated" v "validate => true"

问题描述

似乎在 rails 中，您可以在两个地方定义关联验证，或者在关联本身上:

It seems that in rails you can define association validations in two places, either on the association itself:

class Child

  belongs_to :parent, :validate => true

end

或作为验证回调:

class Child

  belongs_to :parent

  validates_associated :parent

end

这两种方法有什么区别?

What is the difference between these two methods?

测试差异

我认为也许前者会产生背压并强制父级仅在子级有效时才有效:

I thought that maybe the former creates a backpressure and enforces that the parent is only valid if the child is valid:

即(当设置 :validate => true 时)

i.e. (when setting :validate => true)

child.valid? # => false
child.parent.valid? # => also evaluates to false because of the :validate => true condition


# do whatever it takes to make the child valid again
#...
child.valid? # => true
child.parent.valid? # => true

但是我测试了它并且这不会发生.那么这两种方法有什么区别(如果有的话)?

However I tested it and this doesn't happen. So what's the difference (if any) between the two methods?

推荐答案

我不得不深入研究 Rails (3.0.7) 代码以找到一些差异.核心功能在我看来是一样的——它们似乎都在关联的记录上调用 valid?.

I had to dig into the Rails (3.0.7) code to find some differences. The core functionality looks the same to me -- they both seem to call valid? on the associated record(s).

我发现的主要差异仅在使用 :autosave 功能或销毁关联对象或将其标记为销毁时出现.例如，我有:

The key differences that I did find only appear when using the :autosave feature or when either destroying the associated object or marking it for destruction. For example, I have:

class AbsentDate < ActiveRecord::Base
  belongs_to :user, :autosave => true, :validate => true
end

我看到以下行为:

user = User.new(:username => "Jimmy")
user.valid?                               # => true
ad = AbsentDate.new(:user => user)
user.username = nil                          
user.valid?                               # => false
ad.valid?                                 # => false
ad.errors.full_messages                   # => ["User username cannot be empty"]
ad.user.mark_for_destruction
ad.valid?                                 # => true

请注意，将用户标记为销毁会导致有效的 AbsentDate.另请注意，只有一条错误消息.现在考虑这种情况:

Note that marking the user for destruction resulted in a valid AbsentDate. Also note that there is only one error message. Now consider this case:

class AbsentDate < ActiveRecord::Base
  belongs_to :user, :autosave => true
  validates_associated :user
end

这是我所看到的:

user = User.new(:username => "Jimmy")
user.valid?                                # => true
ad = AbsentDate.new(:user => user)
user.username = nil
user.valid?                                # => false
ad.valid?                                  # => false
ad.errors.full_messages                    # => ["User username cannot be empty", "User is invalid"]
ad.user.mark_for_destruction
ad.valid?                                  # => false

这次有两条错误消息，即使其用户已被标记为销毁，AbsentDate 仍然是假的.我能够通过调用 destroy 而不是 mark_for_destruction 来复制这些结果.

Two error messages this time, and the AbsentDate is still false even though its user has been marked for destruction. I was able to replicate these results by calling destroy instead of mark_for_destruction.

最后一件事:如果你使用 validates_related，你会得到几个选项(:if、:unless、:on, :message) 如果您在 belongs_to 上使用标志，您将不会拥有.

One last thing: if you use validates_associated, you get several options (:if, :unless, :on, :message) that you won't have if you use the flag on belongs_to.

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