hello, When I'm learning the rails route system I find this problem.

First, I have all my controllers under the app folder, and I decide to move some of them to a admin under app so change the routes.rb like following
Code Ruby:
map.with_options(:namespace=>"admin") do |admin|
    admin.resources :instruments, :groups, :markets
now I can point my browser to http://localhost:3000/admin/groups and view a list of groups as usual.

But when I point my mouse to those links (new, show, edit, destroy), I find a problem those generated links still pointed to the old location http://localhost:3000/groups

I use new_group_url method to generate links to create a new group.
Code Ruby:
<%= link_to "New Group", new_group_url %>

My question is what is the method that generate proper link url to my nested controllers (http://localhost:3000/admin/groups)?

Thanks you