Q:

Syntax for form_for when building an array from checkboxes

I'm making a form for an Order object, and the order has many Products, via a join table called OrderProducts.  So, we've got something like this:
<% @order = Order.new %>
<% form_for @order do |f| %>
  <% @products.each do |product| %>
    ... want to iterate over products here to build up "order[product_ids][]", with one checkbox per product
  <% end %>
<% end %>

Usually for each product i would have a check_box_tag, saying 
<%= check_box_tag "order[product_ids][]", product.id, @order.product_ids.include?(product.id) %>

But this, while working fine, always feels like a bit of a cop out.  Is there a way i can do it with the f.check_box syntax?  Important note - on the project in question I'm working in Rails 2.2.2, so a solution that works in rails 2 would be ideal.

A:

Rails <= 2.x (original)
<% @products.each do |product| -%>

  <% fields_for 'product[]' , product do |product_fields| -%>

    [...]
    <%= product_fields.check_box :id %>

  <% end -%>

<% end -%>

Rails >= 3.x (updated)
<% @products.each do |product| -%>

  <%= fields_for 'product[]' , product do |product_fields| -%>

    [...]
    <%= product_fields.check_box :id %>

  <% end -%>

<% end -%>

A:

I know the author was looking for version 2 answers, but this is the top hit for google and I though I would update:
One can do this ( I'm using 4.0, don't know how far back it goes ):
<%= form_for @order do |form| %>
  <%= form.collection_check_boxes(:product_ids, Product.all, :id, :labeling_method ) %>
<% end %>

For more info: http://edgeapi.rubyonrails.org...

