Adding Authentication to a Rails App with Devise

In this tutorial, we will be adding authentication to a Rails app using the Devise library. Devise is a popular gem that provides a full-featured and flexible authentication solution for Rails apps.

Step 1: Install the Devise gem

Add the Devise gem to your Gemfile and run the bundle install command to install it.

# Gemfile
gem 'devise'

bundle install

Step 2: Run the Devise installation generator

Run the Devise installation generator to create the necessary files and configuration for Devise.

rails generate devise:install

This generator will create a config/initializers/devise.rb file and add a few lines of code to your config/routes.rb file. It will also provide you with instructions for setting up Devise in your app, such as setting the default URL options and enabling flash messages.

Step 3: Create a Devise model

Run the Devise model generator to create a model for your user. If you already a model that represents a user (such as Person, Traveller or any other) just replace User with the name of your model. In this article I’ll just stick to User.

rails generate devise User

This generator will create a User model and a migration file to add the necessary database columns for Devise.

Step 4: Run the Devise migration

Run the migration to create the necessary database columns for Devise.

rails db:migrate

Step 5: Add Devise views

If you want to customize the views for Devise (e.g., the login and registration forms), you can generate the Devise views and customize them as needed editingi.

rails generate devise:views

Step 6: Add Devise routes

Add the Devise route to your config/routes.rb file.

# config/routes.rb

Rails.application.routes.draw do

  # Add the line below:
  devise_for :users
end

Step 7: Add authentication to your controllers and views

To require authentication for certain actions in your controllers, use the authenticate_user! method. For example:

class DestinationsController < ApplicationController
  before_action :authenticate_user!, only: [:create, :update, :destroy]

  def index
    # display a list of destinations
  end

  def show
    # display a single destination
  end

  def create
    # create a new destination
  end

  def update
    # update an existing destination
  end

  def destroy
    # delete a destination
  end
end

In this example, we are requiring authentication for the create, update, and destroy actions in the DestinationsController. Only authenticated users will be able to access these actions. The index and show actions will still be available for unauthenticated user.

To display a login or logout link in your views, you can use the current_user and user_signed_in? helper methods provided by Devise. The current_user method returns the currently logged-in user, and the user_signed_in? method returns a boolean indicating whether or not a user is signed in.

For example, you can use the following code in a view file to display a login link if the user is not signed in, or a welcome message and logout link if the user is signed in:

<% if user_signed_in? %>
  Welcome, <%= current_user.email %>!
  <%= link_to "Log out", destroy_user_session_path, method: :delete %>
<% else %>
  <%= link_to "Log in", new_user_session_path %>
<% end %>

Conclusion

In this tutorial, we learned how to add authentication to a Rails app using the Devise library. We installed the Devise gem, ran the Devise installation generator, created a Devise model, ran the Devise migration, added Devise views and routes, and implemented authentication in our controllers and views.

With Devise, it is easy to add a full-featured and flexible authentication system to your Rails app. Whether you need simple authentication for a personal project or advanced features for a large-scale application, Devise has you covered.

I hope this tutorial was helpful in getting you started with Devise. If you have any questions or comments, please don’t hesitate to reach out.

Happy coding!