Devise routing issues with admin role - ruby-on-rails

Question

I'm trying to add Devise to an existing Rails 3.2.16 app.
I have the basics working, but I'd like to create an admin role that is able to edit any user profile without entering a password.
I used the code from Option 2 - Adding an admin attribute in the Devise Wiki "Add An Admin Role" section to set up the admin role.
My routes.rb has this:
devise_for :users, :controllers => { :registrations => :registrations }
scope "/admin" do
resources :users
end
This gives me the following routes
new_user_session GET /users/sign_in(.:format) devise/sessions#new
user_session POST /users/sign_in(.:format) devise/sessions#create
destroy_user_session DELETE /users/sign_out(.:format) devise/sessions#destroy
user_password POST /users/password(.:format) devise/passwords#create
new_user_password GET /users/password/new(.:format) devise/passwords#new
edit_user_password GET /users/password/edit(.:format)devise/passwords#edit
PUT /users/password(.:format) devise/passwords#update
cancel_user_registration GET /users/cancel(.:format) registrations#cancel
user_registration POST /users(.:format) registrations#create
new_user_registration GET /users/sign_up(.:format) registrations#new
edit_user_registration GET /users/edit(.:format) registrations#edit
PUT /users(.:format) registrations#update
DELETE /users(.:format) registrations#destroy
admin_edit_user GET /admin/users/:id/edit(.:format) users/registrations#edit
users GET /admin/users(.:format) users#index
POST /admin/users(.:format) users#create
new_user GET /admin/users/new(.:format) users#new
edit_user GET /admin/users/:id/edit(.:format) users#edit
user GET /admin/users/:id(.:format) users#show
PUT /admin/users/:id(.:format) users#update
DELETE /admin/users/:id(.:format) users#destroy
The user views (devise/registrations/edit, etc) are hooked up correctly and work just fine, but the admin views are all pulled from the users folder (users/edit, etc), which means they bypass Devise.
For instance, my admin user edit form should probably have some variation on this in the form_for:
<%= form_for(resource, :as => resource_name, :url => registration_path(resource_name)) do |f| %>
but that code doesn't pull in any of the user data (all form fields are empty). The only way I can get it to show up is with the old code:
<%= form_for #user do |f| %>
Which then uses the update method from my users_controller, NOT from the Devise registrations_controller.
I've tried lots of variations on the routes because that seems to be key, but non of my attempts have worked. Help?

Answer 1

In order for your form_for helper to properly route your request through Devise, you need to declare your admin/users resource routes as Devise routes:
# config/routes.rb
devise_for :users, :controllers => { :registrations => :registrations }
scope "/admin" do
devise_for :users, :controllers => { :registrations => :registrations }
end
You'll continue to retain Devise functionality while being able to utilize the admin namespace for authorization purposes.