Nested Forms and Building associations

I'm working on a add to cart form. It looks something like this

#Models
Order.rb
  has_many :line_items
  accepts_nested_attributes_for :line_items, :allow_destroy => true

LineItem.rb
  has_one :product
  belongs_to :order

Product.rb
  belongs_to :line_item

I'd like to create a form in product#show to allow multiple related products to be added to the order/cart at once, basically create or update a line item for each product.

Probably something like this in the view (HAML to keep it brief).

-form_for @order do |f|
 - if has_related?
   - for related in @products.related_products
     - f.field_for :line_item do |li_form|
       = li_form.text_field :quantity
       = li_form.hidden_field :product_id
       = related.product_name

What would it take开发者_运维知识库 to actually make something like this work?

I would need more info to be sure, but it seems that a LineItem belongs_to :product and Product should NOT belong_to :line_item unless there really is a 1-1 relationship there (which wouldn't make sense to me, and doesn't follow the normal convention of these sorts of systems)

Note** using - before form_for and fields_for has been deprecated in rails 3 in favor of = since the form does actually render html

= fields_for :line_items do |li_form| is the syntax for a has_many relationship

The rest all depends on your user experience design.

Hope this helps!