Rails 3嵌套模型表单，使用位于深层的两个级别accep_nested_attributes_for

Question

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，但是如果Rails能够自动处理它，那么显而易见的原因会更好。

我在做什么错？我试着改变| af |在“字段为：图像做”到它自己的唯一名称，但它没有任何作用。

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

我想你已经得到了表单变量稍微混合起来。它应该是：

= 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 

注意如何form_for ... do |f|滋生f.fields_for ... do |af|，这又滋生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|。