Rails 3 - Nested forms with a has many through association with checkboxes

I am using a has many through association so that an article can be 'saved' to many sections and that relation is called a location. In the locations table there is also a 'default' column (boolean), this allows the user to indicate which section is the default one.

Here are the models:

class Article < ActiveRecord::Base
  has_many :locations
  has_many :sections, :through => :locations

  def default_location
    self.sections.where('locations.default = 1').first
  end
end

class Location < ActiveRecord::Base
  belongs_to :article
  belongs_to :section
end

class Section < ActiveRecord::Base
  has_many :locations
  has_many :articles, :through => :locations
end

So in my view:

<%= form_for(@article) do |f| %>
...
  <p class="field">
     <h3>Locations</h3>
     <ul>
      <% @sections.each do |section| %>
        <li><%= radio_button_tag ???, section.id, :checked => @article.default_location == section %> <%= check_box_tag 'article[section_ids][]', section.id, @art开发者_运维技巧icle.section_ids.include?(section.id), :id => dom_id(section) %><%= label_tag dom_id(section), section.name %></li>
      <% end %>
     </ul>
   </p>
...
<% end %>

So far I can save and update the locations fine but I'm not sure how to assign the default field to each location saved. I have added a radio button for each section so the user can select the default but I'm not sure how to tie it all together.

Any ideas will be really appreciated! Thanks.

---

Not sure why you need both a radio button and check box. Try adding a hidden_field_tag along with a check_box_tag:

  <p class="field">
     <h3>Locations</h3>
     <%= hidden_field_tag "article[section_ids][]", "" %>
     <ul>
      <% @sections.each do |section| %>
        <li>
          <%= check_box_tag :section_ids, section.id, @article.section_ids.include?(section.id), :id => dom_id(section), :name => 'article[section_ids][]' %>
          <%= label_tag dom_id(section), section.name %>
        </li>
      <% end %>
     </ul>
   </p>