Adding customer action for devise - ruby-on-rails

Question

I'm trying to add a simple custom action cancelaccount to a user model generated by devise, but having a hard time getting the routing right.
Here is what's in route.rb
devise_for :users, controllers: { registrations: "userregistrations", sessions: "sessions" } do
get '/users/:id/cancelaccount', to: 'userregistrations#cancelaccount', as: 'cancelaccount'
end
Here is the controller
class UserregistrationsController < Devise::RegistrationsController
def create
...
end
def cancelaccount
authenticate_user!
Rails.logger.debug {"&& cancel"}
#user = User.find(params[:id])
unless (#user == current_user)
redirect_to :back, :alert => "Access denied."
end
end
end
Here is the link_to line in the HTML:
<li><%= link_to "Cancel Account", {controller: "userregistrations", action: "cancelaccount", id: current_user.id} %></li>
This is the error I get:
No route matches {:action=>"cancelaccount", :controller=>"userregistrations", :id=>12}
If I change the link_to link to:
<li><%= link_to "Cancel Account", cancelaccount_path(#user) %></li>
The error is:
undefined method `cancelaccount_path' for #<#:0x00000006a5d4c0>
Any help is highly appreciated.
Here is the result of "rake routes":
new_user_session GET /users/sign_in(.:format) sessions#new
user_session POST /users/sign_in(.:format) sessions#create
destroy_user_session DELETE /users/sign_out(.:format) sessions#destroy
user_omniauth_authorize GET|POST /users/auth/:provider(.:format) devise/omniauth_callbacks#passthru {:provider=>/(?!)/}
user_omniauth_callback GET|POST /users/auth/:action/callback(.:format) devise/omniauth_callbacks#:action
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
PATCH /users/password(.:format) devise/passwords#update
PUT /users/password(.:format) devise/passwords#update
cancel_user_registration GET /users/cancel(.:format) userregistrations#cancel
user_registration POST /users(.:format) userregistrations#create
new_user_registration GET /users/sign_up(.:format) userregistrations#new
edit_user_registration GET /users/edit(.:format) userregistrations#edit
PATCH /users(.:format) userregistrations#update
PUT /users(.:format) userregistrations#update
DELETE /users(.:format) userregistrations#destroy
root GET / static_pages#home
users GET /users(.:format) users#index
POST /users(.:format) users#create
new_user GET /users/new(.:format) users#new
edit_user GET /users/:id/edit(.:format) users#edit
user GET /users/:id(.:format) users#show
PATCH /users/:id(.:format) users#update
PUT /users/:id(.:format) users#update
DELETE /users/:id(.:format) users#destroy
userpreferences GET /userpreferences(.:format) userpreferences#index
POST /userpreferences(.:format) userpreferences#create
new_userpreference GET /userpreferences/new(.:format) userpreferences#new
edit_userpreference GET /userpreferences/:id/edit(.:format) userpreferences#edit
userpreference GET /userpreferences/:id(.:format) userpreferences#show
PATCH /userpreferences/:id(.:format) userpreferences#update
PUT /userpreferences/:id(.:format) userpreferences#update
DELETE /userpreferences/:id(.:format) userpreferences#destroy
signup GET /signup(.:format) devise/registrations#new
edit_profile GET /edit_profile(.:format) devise/registrations#edit
change_password GET /change_password(.:format) devise/passwords#edit
sign_in GET /sign_in(.:format) devise/sessions#new
sign_out GET /sign_out(.:format) devise/sessions#destroy
confirmation GET /confirmation(.:format) devise/confirmations#new
unlock_account GET /unlock_account(.:format) devise/unlocks#new
GET /signup(.:format) trainer/registrations#new
edit GET /edit(.:format) trainer/registrations#edit
GET /sign_in(.:format) devise/sessions#new
GET /sign_out(.:format) devise/sessions#destroy
GET /confirmation(.:format) devise/confirmations#new
GET /unlock_account(.:format) devise/unlocks#new

Answer 1

I am not sure what is wrong with your devise_for block, but you can easily add this route outside of it:
devise_for :users, controllers: { registrations: "userregistrations", sessions: "sessions" }
match '/users/:id/cancelaccount' => 'registrations#cancelaccount', via: 'get', as: 'cancelaccount'
Which will add the route you want:
cancelaccount GET /users/:id/cancelaccount(.:format) registrations#cancelaccount