添加现有的has_many记录与accepts_nested_attributes_for新纪录 [英] Adding existing has_many records to new record with accepts_nested_attributes_for

问题描述

该错误无法找到ID项目= 123支付与ID =添加现有项目的模型，以一种新的支付模式时出现。这是在一个的has_many关系和使用accepts_nested_attributes_for

The error "Couldn't find Item with ID=123 for Payment with ID=" occurs when adding existing Item models to a new Payment model. This is in a has_many relationship and using accepts_nested_attributes_for.

class Payment < ActiveRecord::Base
  has_many :items
  accepts_nested_attributes_for :items
  ...

class Item < ActiveRecord::Base
  belongs_to :payment
  ...

支付和项目模型是假设性的，但问题是真实的。我需要支付的项目（像我这样的新动作）保存支付（在创建动作完成）之前关联。以用户需求为他们所创造的付款修改属性的项目（增加了计费code将是一个例子）。

The payment and item models are hypothetical but the problem is real. I need to associate the Items with the Payment (as I do in the new action) before saving the Payment (done in the create action). The user needs to modify attributes on the Items as they create the Payment (adding a billing code would be an example).

具体而言，在控制器的create动作时出现错误：

Specifically, the error occurs in the controller's create action:

# payments_controller.rb

def new
  @payment = Payment.new
  @payment.items = Item.available # where(payment_id: nil)
end

def create
  @payment = Payment.new payment_params # <-- error happens here
  ...
end

def payment_params
  params.require(:payment).permit( ..., [items_attributes: [:id, :billcode]])
end

的lib / active_record / nested_attributes.rb：543：！raise_nested_attributes_record_not_found在是立即在调用堆栈在它之前。奇怪的是，ActiveRecord的是包括pa​​yment_id作为搜索条件的一部分。

lib/active_record/nested_attributes.rb:543:in 'raise_nested_attributes_record_not_found!' is immediately prior to it in the callstack. It is curious that ActiveRecord is including payment_id as part of the search criteria.

为了被完整，形式看起来是这样的...

For the sake of being complete, the form looks something like this...

form_for @payment do |f|
   # payment fields ...
   fields_for :items do |i|
     # item fields    

和它呈现在正确的项目上的新动作。通过表单传递的PARAMS是这样的：

and it renders the Items correctly on the new action. The params passed through the form look like this:

{ "utf8"=>"✓",
  "authenticity_token"=>"...",
  "payment"=>{
    "items_attributes"=>{
      "0"=>{"billcode"=>"123", "id"=>"192"}
    },
  }
}

如果有更好的方式来处理这种不使用 accepts_nested_attributes_for 我很开放的建议。

If there is a better way to approach this that doesn't use accepts_nested_attributes_for I'm open to suggestions.

推荐答案

这让我困惑...

添加现有记录到一个新的纪录。

"Adding existing records to a new record..."

所以，你必须项目1，2，3 ，并希望它们关联到一个新的产品对象？

So you have Item 1, 2, 3, and wish to associate them to a new Product object?

-

加入型号

要做到这一点会使用加入模型的方式（ 的habtm ），而不是通过的 accepts_nested_attributes_for

The way to do this will be to use a join model (habtm) rather than sending the data through accepts_nested_attributes_for

底线是每次创建一个新的产品对象时，其相关的项目对象可以的只有的关联到该产品：

The bottom line is every time you create a new Product object, its associated Item objects can only be associated to that product:

#items table
id | product_id | information | about | item | created_at | updated_at

所以，如果你想使用现有 项目的对象，如何定义的的多个的关联又在哪里？事实是，你不能 - 你必须创建一个中间表/模型，经常被当作一个加入模型：

So if you're looking to use existing Item objects, how can you define multiple associations for them? The fact is you can't - you'll have to create an intermediary table / model, often cited as a join model:

#app/models/product.rb
Class Product < ActiveRecord::Base
   has_and_belongs_to_many :items
end

#app/models/item.rb
Class Item < ActiveRecord::Base
   has_and_belongs_to_many :products
end

#items_products (table)
item_id | product_id

-

HABTM

如果您使用的是HABTM设置（如我上面所演示的），它可以让你添加/从的 集合 与不同的对象有，还有一个偷偷摸摸的伎俩，你可以再补充产品来使用某产品 item_ids ：

If you use a HABTM setup (as I have demonstrated above), it will allow you to add / delete from the collection your various objects have, as well as a sneaky trick where you can just add Items to a product using item_ids:

#app/controllers/products_controller.rb
Class ProductsController < ApplicationController
   def create
      @product = Product.new(product_params)
      @product.save
   end

   private

   def product_params
       params.require(:product).permit(item_ids: [])
   end
end

如果你那么参数 item_ids [] 传递给你的 create_method ，将填充集合为您服务。

If you then pass the param item_ids[] to your create_method, it will populate the collection for you.

如果你想具体的项目添加到产品或删除它们，你不妨这样做：

If you want to add specific items to a product, or remove them, you may wish to do this:

#app/controllers/products_controller.rb
Class ProductsController < ApplicationController
   def add
     @product = Product.find params[:id]
     @item = Item.find params[:item_id]

     @product.items << @item
     @product.items.delete params[:item_id]
   end
end

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