Ruby-on-rails Rails 3：“accepts_nested_attributes_for”如何工作？
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Rails 3: How does "accepts_nested_attributes_for" work?
提问by Misha Moroshko
Consider the following association:
考虑以下关联：
class Product < ActiveRecord::Base
belongs_to :shop
accepts_nested_attributes_for :shop
end
If
如果
params[:product][:shop_attributes] = {"name" => "My Shop"}
and I do:
我这样做：
@product = Product.new(params[:product])
@product.save
a new shop with name "My Shop" is created and assigned to the @product, as expected.
@product正如预期的那样，一个名为“My Shop”的新商店被创建并分配给。
However, I can't figure out what happens when shop_attributescontains some id, like:
但是，我无法弄清楚当shop_attributescontains some时会发生什么id，例如：
params[:product][:shop_attributes] = {"id" => "20", "name" => "My Shop"}
I get the following error:
我收到以下错误：
Couldn't find Shop with ID=20 for Product with ID=
Question 1
问题 1
What does this means ?
这是什么意思？
Question 2
问题2
If this is the case, i.e. the idof the shop is known, and the shop with such idalready exist, how should I create the @productsuch that this shop will be assigned to it ?
如果是这种情况，即id商店的名字是已知的，并且id已经存在这样的商店，我应该如何创建@product这样的商店将被分配给它？
采纳答案by clemensp
I think that you're trying to figure out creating a new associated item vs. associating with an existing item.
我认为您正在尝试弄清楚创建新的关联项目与与现有项目关联。
For creating a new item, you seem to have it working. When you passed the id in shop_attributes, it did not work, because it's looking up an association that doesn't exist yet.
对于创建新项目，您似乎可以正常工作。当您在 shop_attributes 中传递 id 时，它不起作用，因为它正在查找尚不存在的关联。
If you're trying to associate with an existing item, you should be using the following:
如果您尝试与现有项目关联，则应使用以下内容：
params[:product][:shop_id] = "20"
This will assign the current product's shop to the shop with id 'shop_id'. (Product should have a 'shop_id' column.)
这会将当前产品的商店分配给 ID 为“shop_id”的商店。（产品应该有一个“shop_id”列。）
