How to configure Devise gem for your Ruby on Rails Application (User Authentication)

Devise gem is used to make a simple authentication solution in rails.You no need to create authentication form it will create automatically. Like Username, Password, Signin, Signup, Forgot Password and Remember me.Please follow below steps.

10 Steps for Setup Devise gem in rails application :

 Step 1: Create a new Ruby on Rails Application

      > rails new devexam

      .
 Step 2: Open Gemfile and add the devise gem in Gemfile (devexam/Gemfile)

       gem 'devise'

     
 Step 3: Install newly added gem

      > bundle install

    
 Step 4: Create the Product form with CRUD using scaffold

      > rails g scaffold Product name:string price:integer description:text

 
 Step 5: Apply changes to database.Product table added to database with help of migration.

      > rake db:migrate

 Step 6: Add below lines to routes.rb (devexam/config/routes.rb)

       root 'products#index'

 Step 7: Setup the Devise gem

      > rails generate devise:install

 Step 8: Below command generate the USERS table

      > rails generate devise User

 Step 9: Apply the table changes to database.

      > rake db:migrate

   
    Note : Any error occur means do following steps :
 
 1. Edit the filename in below location (devexam/db/migrate               /20141126085540_devise_create_users) and add extension .rb (20141126085540_devise_create_users.rb)
 2. Now do migrate.
 
 Step 10: Open ApplicationController and add below line. (devexam/app/controller/application_controller.rb)

   class ApplicationController < ActionController::Base
     protect_from_forgery with: :exception
     before_action :authenticate_user!
   end

 Step 11: Now run your application

       > rails server

 Step 12: Add Logout and Edit profile option to your form
      Just copy and paste the below code to index.html.erb (devexam/app/views/products/index.html) or any html file
   

   <ul class="nav navbar-nav navbar-right">

     <li class="dropdown">

       <a class="dropdown-toggle" data-toggle="dropdown" href="#" id="items">

         Account <span class="caret"></span>

       </a>

       <ul class="dropdown-menu" aria-labelledby="items">

        <li>

         <% if user_signed_in? %>

           <strong>&nbsp;<%= current_user.email %></strong>

       <%= link_to 'Edit profile', edit_user_registration_path, :class => 'navbar-link'%>

        </li>

        <li>

         <%= link_to "Logout", destroy_user_session_path, method: :delete, :class => 'navbar-link'  %>

        </li>

        <% else %>

         <li>

        <%= link_to "Sign up", new_user_registration_path, :class => 'navbar-link'%>

         </li>

         <li>

          <%= link_to "Login", new_user_session_path, :class => 'navbar-link' %>

         </li>

       <% end %>

       </ul>

      </li>

    </ul>