立即调用ActiveRecord 39的#relationship_ids = [1,2,3].任何解决方法? [英] Calling ActiveRecord's #relationship_ids = [1,2,3] saves immediately. Any workarounds?
问题描述
我在ActiveRecord的#relationship_ids方法中遇到了一个奇怪的问题(当您声明"has_many"时会自动添加)，该方法会立即保存现有记录，这给我带来了一些问题，我想知道是否有人有任何有用的建议
I've come across an oddity in ActiveRecord's #relationship_ids method (that's added automatically when you declare 'has_many'), which saves immediately for existing records, which is causing me some issues, and I wonder if anyone had any useful advice.
我正在运行Rails 2.3.5.
I'm running Rails 2.3.5.
考虑这种简单的情况，其中文章具有多个标签，例如:
Consider this simple scenario, where an article has_many tags, say:
a = Article.first
a.name = "New Name" # No save yet
a.author_id = 1 # No save yet
a.tag_ids = [1,2,3] # These changes are saved to the database
# immediately, even if I don't subsequently
# call 'a.save'
这让我感到惊讶.在尝试构建预览工具时，这特别导致了问题-我想更新一堆属性，然后在不保存的情况下预览文章-但在这种情况下，即使没有其他字段也可以保存标签更改.
This seems surprising to me. It's specifically causing problems whilst trying to build a preview facility - I want to update a bunch of attributes and then preview the article without saving it - but in this instance the tag changes do get saved, even though no other fields do.
(可能相关的是，如果"a"是一篇新文章，而不是现有文章，那么事情将按照我的预期运行-在我调用"a.save"之前，不会保存任何内容)
(Of possible relevance is that if 'a' is a new article, rather than an existing one, things behave as I'd expect - nothing is saved until I call 'a.save')
我有一个非常讨厌的解决方法-我可以在模型中覆盖tag_ids =方法来代替填充实例变量，然后将相关模型实际保存在before_save回调中.
I have a fairly nasty workaround - I can override the tag_ids= method in my model to instead populate an instance variable, and actually save the related models in a before_save callback.
但是我想知道一种比必须为我想为其创建预览功能的具有has_many关系的每个模型执行此操作更简单的方法.
But I'd love to know of a simpler way than me having to do this for every model with a has_many relationship I'd like to create a preview facility for.
有人有任何修复/解决方法/一般建议吗?谢谢！
Does anyone have any fixes/workarounds/general advice? Thanks!
推荐答案
这是有原因的.称为外键.在具有多个关系的情况下，链接到具有多个模型的信息将作为外键存储在该模型之外.
There's a reason things are this way. It's called foreign keys. In a has many relationship, the information that links to the model that has many is stored outside of that model as a foreign key.
与文章中一样，具有许多标签.将标签链接到商品的信息存储在标签表或联接表中.当您调用文章保存时，您只会保存该文章.
As in Articles, has many tags. The information that links a tag to an article is stored either in the tags table or in a join table. When you call save on an article you're only saving the article.
活动记录会立即修改那些其他记录.除非您正在处理尚未保存的新文章.如果不知道在外键中放置哪个id，Rails将延迟创建/更新关联记录.
Active record modifies those other records immediately. Except in the case where you're working with a new article that hasn't been saved yet. Rails will delay creating/updating the associated records if it doesn't know which id to place in the foreign key.
但是，如果您要修改现有记录，那么您所决定的解决方案实际上就是您可以做的所有事情.甚至有一个使用accepts_nested_attributes_for的骇客，但这确实不值得.
However, if you're modifying existing records, the solution you've decided on is really all that you can do. There's an even uglier hack using accepts_nested_attributes_for, but it's really not worth the effort.
如果您希望将此行为添加到许多模型中，而不是所有模型中，则可能需要考虑编写一个简单的插件来重新定义所需的方法，并在单个类方法调用中添加该回调.看一下act_as_audited之类的来源，看看它是如何完成的.
If you're looking to add this behaviour to many models but not all models, you might want to consider writing a simple plugin to redefine the assigment the method you need and add the call back in a single class method call. Have a look at the source of something like acts_as_audited to see how it's done.
如果您希望将此行为添加到所有模型中，则可以为has_many写一个包装器.
If you're looking to add this behaviour to all models, you can probably write a wrapper for has_many to do that.
这篇关于立即调用ActiveRecord 39的#relationship_ids = [1,2,3].任何解决方法?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！
