devise:Add new user by existing user in rails - ruby-on-rails-4

Question

In a rails project, I use devise to manage my user. Now I want remove sign up from login-page and just user that allready exist, can register new user.
What the best way to do this?

Answer 1

To remove the sign up link from the login page, install the Devise Views and remove that link from the "shared/links" partial.
In your terminal, generate the Devise views:
$ cd path/to/app
$ rails generate devise:views users
In the folder views/devise that is created, edit the document shared/_links.html.erb to contain only the links you want to show.
To allow only existing users to create new users, you will want to at least place restrictions on the Devise::RegistrationsController controller actions new and create. This is a bit complex, and requires creating a custom Devise registrations controller.
To do that, create a file in your controller folder called registrations_controller.rb, and update your routes.rb file to point devise_for :users to that new controller. To restrict actions to signed in users only consider using the Devise helper "authenticate_user!". All of those suggestions together might look like this:
#controllers/registration_controllers.rb
class RegistrationsController < Devise::RegistrationsController
before_action :authenticate_user!, only: [:new, :create]
def new
super
end
def new
super
end
end
And your routes
#config/routes.rb
devise_for :users, :controllers => { :registrations => "registrations" }
Ideally, in the views, Users who are not signed in should not even be given the option to try to create new users, so there should be some additional view logic, such as this:
<% if user_signed_in? %>
<%= link_to "New user", new_user_registration_path %>
<% end %>
To clean up your view, you might consider extracting conditional view logic like this into helpers.
With this setup, existing users will be able to create new users through the new_user_registration_path.
For more information, the Devise documentation is pretty useful (https://github.com/plataformatec/devise) as well as perusing other StackOverflow answers.