What is Devise?

Devise is a flexible authentication solution for Rails. It provides ready-made features for user authentication, such as sign-up, login, and session management. It helps to easily add secure user authentication to a Rails application.

Why Use Devise?

• Easy Integration: Devise is widely used for user authentication in Rails applications and integrates smoothly with Rails.
• Built-in Authentication Features: Devise comes with essential features like login/logout, user registration, password resets, and account management.
• Security: Devise handles security issues like session hijacking, making authentication safer for your application.

Installation & Setup

• Devise is already included in your Gemfile under the :development and :test groups:

  group :development, :test do
    gem "devise"
  end
  

• Run bundle install to install the gem.

• After installing the gem, run the Devise install generator to set up the necessary configurations:

  rails generate devise:install
  

  This will create the following:

  • config/initializers/devise.rb: Configuration file for Devise.
  • Flash message support in views.
  • Devise mailer configurations.
  • Some recommendations (like setting a root route and ensuring default URL options).

• To create the User model with Devise’s built-in authentication, run:

  rails generate devise User
  

• Run migrations to update the database with the users table:

  bin/rails db:migrate
  

How Devise Works in the Finance Tracker App

• User Authentication: Devise handles the login and registration process. Users must sign up and log in to access the app’s features.

• Protecting Routes: In controllers like ExpensesController, we use before_action :authenticate_user! to ensure that only logged-in users can access certain pages.

• Expense Association: Each expense is linked to a user. This ensures that users can only see their own expenses.

• Example of how we protect the routes using Devise:

  class ExpensesController < ApplicationController
    before_action :authenticate_user!  # Ensures only logged-in users can access these routes
  
    # Other actions for handling expenses
  end
  

• Devise Routes: Devise automatically provides routes for user registration, login, and logout. You can find the login page at /users/sign_in, and the sign-up page at /users/sign_up.

• Example of how we add authentication links in the view:

  <%= link_to "Sign up", new_user_registration_path %>
  <%= link_to "Log in", new_user_session_path %>
  <%= link_to "Log out", destroy_user_session_path, method: :delete %>
  

How to Customize Devise Views

Devise provides default views for sign-up, login, and other authentication-related pages. If you want to modify the appearance or functionality of these pages, you can customize them by editing the files in app/views/devise/.

Troubleshooting Common Issues

Here are some common issues you might encounter with Devise and how to resolve them:

• "Invalid Email or Password" Error: If you're getting this error when trying to log in, make sure your email and password are correct. If you're using a development database, check the User model to ensure that it has the necessary fields (like email and encrypted_password).

• Devise Routes Not Working: If you encounter issues with the Devise routes (e.g., new_user_session_path or destroy_user_session_path), ensure that Devise is properly initialized in your application by checking the config/initializers/devise.rb file and ensuring it's been loaded correctly.

• Request Specs Failing with Devise Authentication: If you're facing issues in your request specs where Devise authentication doesn't work (e.g., sign_in not working), ensure that you have the following in rails_helper.rb:

  config.include Devise::Test::IntegrationHelpers, type: :request
  

  If you're still encountering issues, remember to reload routes in rails_helper.rb before running the tests:

  Rails.application.reload_routes!
  

• Database Errors in Tests: When running tests, make sure you’ve migrated your test database properly:

  rails db:test:prepare
  

  If you’ve created new Devise fields (like :email, :password), ensure those fields are included in your test database.