Combine RESTful routes with DataMapper

Hi

I am writing an app in Rails 2 using DataMapper as ORM. It works fine but an unexpected downside is that generated RESTful routes does not work. In Rails 2 you can for example write:

edit_product_path(product)

and it will use the id attribute of product to generate the URL. This no longer works because I assume that it relies on some ActiveRecord feature that DataMapper does not suppy. It can be solved by writing:

edit_product_path(product.id)

which is simple enough but it also applies to redirect_to for which the solution is a bit more elaborate. Besides having to change a lot of code in the resource scaffolds I really like the compact way of handling routes automatically, so my question is this:

What part of Rails is responsible for making the routes work and can it be extended in DataMapper in some way?

Kindest regards

Erik Lindblad