CSC/ECE 517 Spring 2016/Refactor review mapping controller.rb

Devise is a rack based full-fledged authentication system for Rails. It is a complete MVC solution meaning it can support various models, views and controllers as part of its code and can be used be directly by developers. Devise is simple to use and starts up with a couple of commands but it is also highly customizable. Devise saves a lot of time and effort as many applications require user registration and authentication mechanisms which are difficult to develop from scratch.

History

Devise is first introduced in January 2010 by Plataformatec, a company which builds web and mobile applications. Devise is one of the few authentication systems which support rack based applications and hence can support Rails 3 and up as they are completely rack based. The latest version of Devise available is v3.5.3 and it is up to date to Rails 5 beta 2.

Installation

Although Devise is very useful and reduces the amount of effort in developing authentication mechanisms significantly, it requires a good understanding of the Rails framework. Hence it is advised for beginners to not use Devise.

There are several commands that are required for the successful installation of Devise. They are listed out below:

• Add the devise gem to your gemfile.

gem 'devise'

• Run bundle command to install the gem.

bundle install

• You need to run the generator next which will install an initializer and creates all the configuration files.

rails generate devise:install

• Now you can add Devise to any of your models using the generator. This will create a class with the model name given and routes etc. The model will be configured with default Devise modules. The config/routes.rb file will be configured to point to the Devise controller.

rails generate devise user //Assuming that the model name is user

• Next, add any configuration changes that are required and then run:

rake db:migrate

• The following step will create Devise views but is optional. Devise has views for every generic operation like Login or SignUp and can be used directly instead of creating custom views.

rails generate devise:views users

Modules

There are 10 modules listed on the official page of Devise by Platformatec. These modules are features that are contained in Devise and can be used by the developers depending on the use-cases or requirements of their application. Below is the list of modules:

• Database Authenticable
• Omniauthable
• Confirmable
• Recoverable
• Registerable
• Rememberable
• Trackable
• Timeoutable
• Validatable
• Lockable

Methods

There are many classes in Devise which include models, controllers, helpers, views, routes etc. But much of the functionality offered by Devise is exposed via simple helper methods. Some of the most important methods which can be used in building our own application are:

• authenticate_user! : This method is used to check whether a user is logged in before he/she attempts to perform a specific set of controller actions. authenticate_user! may be called with before_action as shown below to ensure the user is logged in before performing any of the operations.

before_action :authenticate_user!

If only some of the actions need authentication and some do not, we can use except clause so that only some actions are blocked as guest and others are accessible. The code with except clause is as below:

before_action :authenticate_user! except [:index, :show]

In the above example index and show are two controller actions associated with operations which do not require user authentication and can be browsed as a guest.Authenticate user may also be used with in a controller action so that it is application only for that specification. We need to use before_filter instead of before_action to achieve this purpose:

• current_user
• user_signed_in?
• signed_in(@user)
• sign_out(@user)
• user_session

References

• Object-Oriented Design and Programming