Rails 3嵌套模型表单，使用accep_nested_attributes_for深入2级

问题描述

我的嵌套模型表单在第一层深处工作良好。但我的印象是，你可以使用accept_nested_attributes_for深入多层次。但是，当我尝试下面的代码时，图像属性被附加到顶级问题模型，并且在表单提交时中断了未知属性图像错误。

我可以使用表单数据手工完成插入操作，但如果Rails能够自动处理它，则会因为显而易见的原因而更好。

我做错了什么？我试着改变| af |在字段为：图片做为其自己的唯一名称，但它没有任何效果。

型号：

  class问题< ActiveRecord :: Base 
 has_one：answer 
 accep_nested_attributes_for：answer 
 end 
 
 class答案< ActiveRecord :: Base 
 belongs_to：问题
 has_one：图片
 accep_nested_attributes_for：图片
结束
 
图片< ActiveRecord :: Base 
 belongs_to：answer 
 end 
  

控制器：

  def new 
 @question = Question.new 
 answer = @ question.build_answer 
 image = answer .build_image 
 
 @case_id = params [：id] 
 
 render：layout => 'application'，：template => '/ questions / form'
 end 
 
 def create 
 question_data = params [：question] 
 @question = Question.new（question_data）
 if @ question.save 
 ... 
 end 
  

查看：

  = form_for @question，：html => {：multipart => true} do | f | 
 
 = f.label：text，问题文本：
 = f.text_area：text，：rows => 7 
 
％br 
％br 
 
 = f.fields_for：answer，do | af | 
 = af.label：body，Answer Text：
 = af.text_area：body，：rows => 7 
 
％br 
％br 
 
 = f.fields_for：image do | af | 
 = af.label：title，Image Title：
 = af.text_field：title 
 
％br 
 
 = af.label：file ，Image File：
 = af.file_field：file 
 
％br 
 
 = af.label：caption，Image Caption：
 = af.text_area：caption，：rows => 7 
 
 = hidden_​​field_tag（case_id，value = @case_id）
 
 = f.submit 
  

解决方案

我认为你已经将表单变量稍微混合起来了。它应该是：

  = form_for @question，：html => {：multipart => true} do | f | 
 
 = f.label：text，问题文本：
 = f.text_area：text，：rows => 7 
 
％br 
％br 
 
 = f.fields_for：answer，do | af | 
 = af.label：body，Answer Text：
 = af.text_area：body，：rows => 7 
 
％br 
％br 
 
 = af.fields_for：image do | img_form | 
 = img_form.label：title，Image Title：
 = img_form.text_field：title 
 
％br 
 
 = img_form.label：file ，Image File：
 = img_form.file_field：file 
 
％br 
 
 = img_form.label：caption，Image Caption：
 = img_form.text_area：caption，：rows => 7 
 
 = hidden_​​field_tag（case_id，value = @case_id）
 
 = f.submit 
  

注意 form_for ... do | f | spawns f.fields_for ... do | af | ，然后产生 af.fields_for ... do | img_form | 。

关键是第二个fields_for。它应该是 af.fields_for：image do | img_form | 而不是 f.fields_for：image do | img_form | 。

My nested model form is working great on the first level deep. But I was under the impression that you could go many levels deep using accepts_nested_attributes_for. But when I try the code below, the "Image" attributes are attached to the top level "Question" model and it breaks upon form submission with an unknown attribute "Image" error.

I could do the inserts all by hand using the form data but if Rails can handle it automatically, it would be better for obvious reasons.

What am I doing wrong? I tried changing |af| in the "fields for :image do" to its own unique name but it didn't have any effect.

Models:

class Question < ActiveRecord::Base
  has_one :answer
  accepts_nested_attributes_for :answer
end

class Answer < ActiveRecord::Base
  belongs_to :question
  has_one :image
  accepts_nested_attributes_for :image
end

class Image < ActiveRecord::Base
  belongs_to :answer
end

Controller:

def new
    @question = Question.new
    answer = @question.build_answer
    image = answer.build_image

    @case_id = params[:id]

    render :layout => 'application', :template => '/questions/form' 
end

def create
  question_data = params[:question]
  @question = Question.new(question_data)
  if @question.save
  ...
end

View:

= form_for @question, :html => {:multipart => true} do |f|

  = f.label :text, "Question Text:"
  = f.text_area :text, :rows => 7

  %br
  %br

  =f.fields_for :answer, do |af|
    = af.label :body, "Answer Text:"
    = af.text_area :body, :rows => 7

    %br
    %br

    = f.fields_for :image do |af|
      = af.label :title, "Image Title:"
      = af.text_field :title

      %br

      = af.label :file, "Image File:"
      = af.file_field :file

      %br

      = af.label :caption, "Image Caption:"
      = af.text_area :caption, :rows => 7

  = hidden_field_tag("case_id", value = @case_id)

  = f.submit

解决方案

I think you've got the form variables slightly mixed up. It should be:

= form_for @question, :html => {:multipart => true} do |f|

  = f.label :text, "Question Text:"
  = f.text_area :text, :rows => 7

  %br
  %br

  =f.fields_for :answer, do |af|
    = af.label :body, "Answer Text:"
    = af.text_area :body, :rows => 7

    %br
    %br

    = af.fields_for :image do |img_form|
      = img_form.label :title, "Image Title:"
      = img_form.text_field :title

      %br

      = img_form.label :file, "Image File:"
      = img_form.file_field :file

      %br

      = img_form.label :caption, "Image Caption:"
      = img_form.text_area :caption, :rows => 7

  = hidden_field_tag("case_id", value = @case_id)

  = f.submit

Notice how form_for ... do |f| spawns f.fields_for ... do |af|, which in turns spawns af.fields_for ... do |img_form|.

The key is the second fields_for. It should be af.fields_for :image do |img_form| rather than f.fields_for :image do |img_form|.

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