validates_linked 不检查关联的存在
谁能弄清楚这里发生了什么事吗？我能够让我的代码按照我想要的方式工作，但我无法弄清楚为什么 validates_linked 没有按我的预期工作。这是我的代码片段：
class Flag < ActiveRecord::Base
belongs_to :user
belongs_to :post
# allow only one flag per post per user
validates_uniqueness_of :user_id, :scope => :post_id
validates :user_id, :post_id, :presence => true
validates_associated :user, :post
attr_accessible :user_id, :post_id
end
使用此代码，我无法保存 user_id == nil 的标志。我可以保存 user_id == 12345 的标志（即某些 user_id 不在数据库中）。 validates_linked API 规范是这样说的：
validates_linked(*attr_names)
验证关联的一个或多个对象本身是否都有效。与任何类型的协会合作。
...
注意：如果尚未分配关联，则此验证不会失败。如果要确保关联既存在又保证有效，还需要使用 validates_presence_of。
相反，我能够通过使用它来获得所需的行为：
validates :user, :post, :presence => true
我对 API 规范的理解是，validates_linked 检查关联表以查看是否存在 id 与 Flag 的外键匹配的行，前提是外键是非零。谁能对此提供任何见解？我是否误解了 validates_linked 应该如何工作？
Can anyone figure out what's going on here? I was able to get my code to work the way I want it to, but I can't figure out why validates_associated isn't working as I expect. Here's a snippet of my code:
class Flag < ActiveRecord::Base
belongs_to :user
belongs_to :post
# allow only one flag per post per user
validates_uniqueness_of :user_id, :scope => :post_id
validates :user_id, :post_id, :presence => true
validates_associated :user, :post
attr_accessible :user_id, :post_id
end
With this code I can't save a flag with user_id == nil. I can save a flag with user_id == 12345 (i.e. some user_id not in the database). This is what the validates_associated API specification says:
validates_associated(*attr_names)
Validates whether the associated object or objects are all valid themselves. Works with any kind of association.
...
NOTE: This validation will not fail if the association hasn’t been assigned. If you want to ensure that the association is both present and guaranteed to be valid, you also need to use validates_presence_of.
I was able to get the desired behavior by using this, instead:
validates :user, :post, :presence => true
My understanding of the API specification is that validates_associated checks the associated table to see if a row exists with an id matching the foreign key of Flag provided the foreign key is non-nil. Can anyone offer any insight on this? Am I misunderstanding how validates_associated is supposed to work?
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validates_linked只是运行关联对象的类中指定的验证，它对外键不执行任何操作。validates :user_id, :presence=>true确保标记记录中存在user_id，但仅此而已。validates :user, :presence=>true用于关联本身，并确保正确设置外键。validates_associatedsimply runs the validations that are specified within the associated object's class, it does nothing in regard to foreign keys.validates :user_id, :presence=>trueensures the presence of auser_idin your flag record, but that's all.validates :user, :presence=>trueis used on the association itself and ensures that foreign keys are properly set up.伙计...我得到的只是需要
validates_presence_of才能像您从 API 中获得的那样工作。检查关联有效性似乎有点矫枉过正，但我是个菜鸟。Man... all I got was that
validates_presence_ofis needed for this to work as you got from the API. Seem's overkill to be checking for association validness, but I'm a noob.