Rails - array of checkboxes

Here is a quick hacky way to make an array of check boxes for a rails form.

Warning: This version of the code hasnt been tested. It most likely needs some debug.

class ModelB  < ActiveRecord::Baseclass
  attr_accessor :name
  attr_accessor :value
end

class ModelA < ActiveRecord::Baseclass
   has_many :model_bs
end

<% form_for( @model_a,
             :url  => {:action => 'new' }, 
             :html => {:method => :post } ) do |form| %>
  <ul class="checkbox_array">
    <% ModelB.find(:all, :order => 'position asc').each do |item| %>
    <li>
      <%= check_box_tag 'model_a[model_b_ids][]', item.id,
          form.object.model_bs.include?(item), 
          { :id => "model_a_model_b_ids_#{item.id}" } %>
      <label for="<%= "model_a_model_b_ids_#{item.id}" %>"><%= h(item.name) %></label>
    </li>
    <% end %>
  </ul>
  <%= submit_tag t('New') %>
<% end %>