Rails 3嵌套模型表单，使用accepts_nested_attributes_for深2层

Question

我的嵌套模型表单在第一层深度上运行良好。但我的印象是，您可以使用 Accept_nested_attributes_for 深入许多层次。但是当我尝试下面的代码时，“图像”属性附加到顶级“问题”模型，它在表单提交时中断，出现未知属性“图像”错误。

我可以使用表单数据手动完成所有插入操作，但如果 R​​ails 可以自动处理它，那么显然会更好。

我做错了什么？我尝试改变 |af|在“：image do”的字段中为其自己的唯一名称，但它没有任何效果。

型号：

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

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, "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

Answer 1

我认为您将表单变量稍微混淆了。应该是：

= 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

注意form_for ... do |f| 是如何产生f.fields_for ... do |af| 的，而af.fields_for ... do |img_form| 又是如何产生的。

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|。