gistfile1.rbx

Merb::Router.prepare do |r|
  r.resources :users do |u|
    u.resources :comments
  end
end

# --- Will use @comment.id and @comment.user_id
url(:user_comment, @comment) # => /users/123/comments/321
# --- Knows the order of arguments in the route and assigns values accordingly
url(:user_comment, @comment.user, @comment) # => /users/123/comments/321
url(:user_cmment, @comment.user, @comment, :xml) # => /users/123/comments/321.xml


url(:user_comment, @comment)
url(:user_cmment, @comment.user, @comment, :xml)