Rails-以“更新”形式显示嵌套属性

Question

I am having a bit of difficulty getting my "update form" to display the nested attributes. Specifically, images (eg, "choices") to display. All other data fields are showing. Just not this is my form:

<%= bootstrap_form_for @template, :url => {:action => 'update', :id => @template.id } do |f| %>
 <fieldset>
  <legend>Update Your Template</legend>
  <%= f.text_field :prompt, :class => :span6, :placeholder => "Which one is running?", :autocomplete => :off %>
  <%= f.select 'group_id', options_from_collection_for_select(@groups, 'id', 'name', selected: @template.group.id) %>
   <div class="row-fluid">
    <ul class="thumbnails">
      <%= f.fields_for :template_assignments do |builder| %>
       <li class="span3" id="">
         <div class="thumbnail">
           <%= builder.text_field :choice_id %>
           <%= image_tag @template.template_assignments.builder.choice.image %>
         </div>
        </li>
      <% end %>
     </ul>
   </div>
 <% end %>

The main line I am having trouble with is:

<%= image_tag @template.template_assignments.builder.choice.image %>

I cannot get it to iterate through each of the 4 nested attributes for the image. It iterates through the 4 nested attributes pertaining to :choice_id, which displays correctly in the text_field.

If i change it to:

<%= image_tag @template.template_assignments.first.choice.image %> , it displays the first image no problem.

However, I need it to iterate and display the "first", "second", "third", and "fourth" images.

Any help on how to display these images, just as the image_id's are being displayed?

EDIT: Here are my models

# app/models/template.rb

class Template < ActiveRecord::Base
 belongs_to :group
 has_many :template_assignments, dependent: :destroy
 has_many :choices, :through => :template_assignments
 accepts_nested_attributes_for :template_assignments, allow_destroy: true
end

# app/models/template_assignment.rb

class TemplateAssignment < ActiveRecord::Base
 belongs_to :template
 belongs_to :choice
end

# app/models/choice.rb

 class Choice < ActiveRecord::Base
  has_many :template_assignments
  has_many :templates, :through => :template_assignments
end

Answer 1

You'll probably want to just use builder directly, just like you're doing in the text_field .

<%= image_tag builder.choice.image %>

[UPDATE] after some trial and error the correct form would be :

<%= image_tag builder.object.choice.image %>

What's happening is that when f.fields_for :template_assignments do |builder| is used to render the nested items, the builder object that is yield ed to the block is not the object itself (in this case a TemplateAssignment ), but is a FormBuilder object, which is what supplies the convenience methods like builder.text_field . (If you tried to do template_assignment.text_field you'd get an error.) The builder stores the object that it is representing in the form as object , so you can get a hold of your template_assignment object by using builder.object . From there you can deal the the template_assignment like normal. I hope that helps.