Create Devise User from Admin Namespace in Rails 5.1 - ruby-on-rails

Question

I have an admin namespaced route for a custom dashboard in my app. I have at least 8 models working, with error free crud operations--all except one. I am using the Devise Gem for user management and a User model. I have the User model in the admin namespace and the only operation I can get to work is changing role and destroy, but I can't create a new user from the dashboard. When I try to create a new user; I get the error "You are already signed in.".
controllers/admin/users_controller.rb
class Admin::UsersController < ApplicationController
before_action :authenticate_user!
before_action :admin_only, :except => :show
def index
#users = User.all
end
def show
#user = User.find(params[:id])
unless current_user.admin?
unless #user == current_user
redirect_to root_path, :alert => 'Access denied.'
end
end
end
def create
#user = User.new
end
def update
#user = User.find(params[:id])
if #user.update_attributes(secure_params)
redirect_to users_path, :notice => 'User updated.'
else
redirect_to admin_users_path, :alert => 'Unable to update user.'
end
end
def destroy
#user = User.find(params[:id])
user.destroy
redirect_to admin_users_path, :notice => 'User deleted.'
end
private
def admin_only
unless current_user.admin?
redirect_to root_path, :alert => 'Access denied.'
end
end
def secure_params
params.require(:user).permit!
end
end
models/user.rb
class User < ApplicationRecord
enum role: [:user, :admin]
def set_default_role
self.role ||= :user
end
devise :database_authenticatable, :registerable,
:recoverable, :rememberable, :trackable, :validatable
end
views/admin/users/new.html.erb
<%= form_for User.new do |f| %>
<div class="form-group">
<%= f.label :first_name %><br/>
<%= f.text_field :first_name, autofocus: true %>
</div>
<div class="form-group">
<%= f.label :last_name %><br/>
<%= f.text_field :last_name %>
</div>
<div class="form-group">
<%= f.label :email %><br/>
<%= f.email_field :email %>
</div>
<div class="form-group">
<%= f.label :password %>
<% if #minimum_password_length %>
<em>(<%= #minimum_password_length %> characters minimum)</em>
<% end %><br/>
<%= f.password_field :password, autocomplete: "off" %>
</div>
<div class="from-group">
<%= f.label :password_confirmation %><br/>
<%= f.password_field :password_confirmation, autocomplete: "off" %>
</div>
<div class="form-group" style="margin-top: 1em">
<%= f.submit 'Sign up', class: 'btn btn--primary type--uppercase inner-link' %>
</div>
<% end %>
views/admin/users/new.html.erb (other method)
<%= form_for([:admin, #user]) do |f| %>
This is how all my name spaced forms are setup but this gives me the error First argument in form cannot contain nil or be empty
routes.rb
...
namespace :admin do
get '', to: 'dashboard#index', as: '/'
resources :pages
resources :articles
resources :categories
resources :tags
devise_for :users
resources :users
resources :albums
resources :banners
resources :products do
resources :variations
end
end
...

Answer 1

using the registration#create action is the appropriate architecture for this?
Because that action is built on a different concept, that the user is not logged in and there are a series of checks for that.
views/admin/users/new.html.erb
you are using registration#new controller action, which does not have the #admin valorized.
def new
#admin = Admin.find(params[:admin_id])
....
end
That is why you get the error, also this approach is not correct.
User will need to register with the traditional devise router, then you will also have to create a nested router for admins to create new users.
this is your link to the admin user registration#new
Your current view/controller#action has the #admin = Admin.find(params[:id]) valorized and the view has the following link
link_to new_admin_user_path(:admin, :user)
the new_admin_user_path is for url /admin/:admin_id/users/sign_up(.:format) that you define in your nested routes.
Step 2) decide which controller#action to use
Do you want to use the standard users/registrations#create or use a new action for this?
I believe you should enhance users/registrations#create by generating the controllers actions in your app as described in devise guide
then in devise controller registrations
def new
#admin = Admin.new(:params[:admin_id]) if params[:admin_id].present?
end
your registrations#new and #create will still trigger errors, you will have to read how devise creates this users by reading their amazing sourcecode and rdoc documentation, modify the process accordingly so that admins can create users by using that action otherwise the less DRY alternative is creating a new controller#action and using it to call an existing User method or a method you will create in the User model to create users. In the end it a User is just an entry in your users database table. Just creating in a similar fashion to other users. As the admin is creating the temporary password, encryption/security issues are not anymore that important. The User will have to change the password anyway.