The default routes of a resource do not let you *modify* a resource partially.

routes.rb

MyApp::Application.routes.draw do
  resources :users`
end

routes_defined

              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
                    PUT    /users/:id(.:format)                    users#update
                    DELETE /users/:id(.:format)                    users#destroy