Accessing url_for from a custom helper classccdaææææøøøæøæ"¥00

I have some custom helper classes under lib/ that need to access the routes (link_to/url_for/etc):
http://gist.github.com/520529

But when I call <%= magic_link Product.first %> from the view it renders the error

Gudleik Rasch wrote in post #966781:

I have some custom helper classes under lib/ that need to access the
routes (link_to/url_for/etc):
http://gist.github.com/520529

But when I call <%= magic_link Product.first %>

NEVER DO THAT! Product.first does a database call. Therefore, it
should *never* be used in the view. The view should never, ever touch
the database under any circumstances. Instead, make the database call
in the controller and set an @instance variable.

from the view it renders

the error

What error?

You'll probably need to include ActionController::UrlWriter in your
helper.

Best,