Devise is an authentication solution which can be used to provide login and logout functionality for your users. This tutorial will explain how to create a Rails app from scratch, with Devise authentication.

Let’s begin

Start by creating a new Rails application. I will name my app blog, however, feel free to name yours as you wish. Make sure you have Ruby, SQLite3, Node.js, Yarn and Rails installed. You can verify these installations using the following commands.

ruby --version
sqlite3 --version
node --version
yarn --version
rails --version

Once you have verified the installation of the prerequisites, create a new Rails app.

rails new blog

Verify that your app is working by starting the Rails server.

bin/rails s

Do Some Modeling

Our simple app will need one model to work properly, a User. The User is the entity which will login and logout from our app. Generate the User model using the Rails generator.

bin/rails g model User first_name:string last_name:string

A file will be created, named app/models/user.rb. Rails will also generate a migration. Let’s run that migration.

bin/rails g db:migrate

The migration will create a table in the sqlite3 database. You can view that table by loading the database

sqlite3 db/development.sqlite3

In the Sqlite3 intepreter, enter the following command

>> .tables

Voila! There is a users table.

Integrate Devise

Now we can integrate Devise. Add the following to your Gemfile:

gem 'devise'

Install the Gem using bundle install. Now run the Devise generator:

bin/rails g devise:install

The generator will provide a set of instructions to your console. The first thing we need to do is add an option to config/environments/development.rb.

config.action_mailer.default_url_options = { host: 'localhost', port: 3000 }

The Devise generator will also have created a migration for us. Let’s run that migration using the command bin/rails db:migrate.

Get it Under Control

Next, let’s create a home controller, and an associated route in config/routes.rb. Create a new file and save it to app/controllers/home_controller.rb. Notice the authenticate_user! method which we are specifying at the top of the controller. By doing this, we are ensuring that the user needs to be logged in to view the content.

# app/controllers/home_controller.rb

class HomeController < ApplicationController
  before_action :authenticate_user!

  def index
    render "home/index"

We will also need to create an associated view, app/views/home/index.html.erb. Let’s populate this file with the following content. Notice the ERB tag, which is going to pull a variable from our controller into the view. In this case, I want to pull the current_user so that we can verify in the view that there is a current_user selected.

<h1>Welcome to My Amazing Website!</h1>

<%= current_user %>

Finally, let’s add notices to our app/views/layouts/application.html.erb. Notice I abbreviated the middle of the file to keep this article short. Don’t delete anything from your file, just copy the two lines with notice and alert.

    <p class="notice"><%= notice %></p>
    <p class="alert"><%= alert %></p>

    <%= yield %>

Look at the View

Finally, let’s use Devise to generate some login and signup views!

bin/rails g devise:views

Launch the server and enjoy your new app!

bin/rails s