rails has_many_through with checkboxes

Photo-components view.png

photo.rb

# extract from photo.rb 
#  after the first two has_manys, the rest are needed for STI, a component can be a base, capital, shaft, column or letterbox

      belongs_to :product
      belongs_to :page, :inverse_of => :photos,  :foreign_key => 'page_id'

      has_many :assignments
      has_many :components,  :through => :assignments
      has_many :bases,       :through => :assignments, :foreign_key=>'component_id'
      has_many :shafts,      :through => :assignments, :foreign_key=>'component_id'
      has_many :capitals,    :through => :assignments, :foreign_key=>'component_id'
      has_many :columns,     :through => :assignments, :foreign_key=>'component_id'
      has_many :letterboxes, :through => :assignments, :foreign_key=>'component_id'

      before_destroy {|photo| photo.components.clear}

product_components.html.erb

<!-- A photo shows several components (which have been put together)  -->
<!-- A series is a product line, and all the components in a series are compatible with each other -->
<!-- When setting up, the user selects which Series is shown in a photo, then selects the exact components shown in the photo. -->
<!-- Components are divided into several types (using STI) so when displaying them we set up a set of checkbox for each component_type-->

<!-- Found it hard to use 'series' as a singular model name, and what is the plural anyway, so settled for 'product' instead -->

<!-- If you ignore all the fussing around with comp_type_name etc, the real work is done at line 24 with f.collection_checkboxes -->

<!-- show a set of components for a series selected for a photo  -->
<!-- series=product, photo -->
<div id="selectComponents"

  <%= simple_fields_for :photo	 do |f| %>
    <h1>Select <%= series.name%> Components</h1>
    <% Refinery::Caststone::Component::COMP_TYPES.each do |comp_type|
        comp_type_name=comp_type.pluralize
        comp_type_method = comp_type_name.downcase
        comp_ids = "#{comp_type}_ids".downcase
        if series.send(comp_type_method).any?  %>
          <fieldset id="<%= comp_type%>" class="component_type">
            <legend>
              <%= comp_type%>
            </legend>
             <%= f.collection_check_boxes comp_ids, series.send(comp_type_method), :id, :name %>
             <%= link_to "Clear #{comp_type_name}", '#', :id => comp_type_name, :class=> 'button clearRadioSet'%>
          </fieldset>
        <%end%>
      <%end%>
     <a id="redraw_button" class="button" href="#" tooltip="Redraw with the currently selected components ">Redraw</a>
  <%end%>
</div>