Facebook authentication with devise in ruby on rails

Step 1: Preparing your Application

   rails new omniauth-tutorial And integrate devise

Step 2: Creating a Provider 

In order to add a provider to Omniauth, you will need to sign up as a developer on the provider’s site. Once you’ve signed up, you’ll be given two strings (sort of like a username and a password), that needs to be passed on to Omniauth. If you’re using an OpenID provider, then all you need is the OpenID URL.
If you want to use Facebook authentication, head over to developers.facebook.com/apps and click on “Create New App”.

Fill in all necessary information, and once finished, copy your App’s ID and Secret.

Configuring Twitter is a bit more complicated on a development machine, since they don’t allow you to use “localhost” as a domain for callbacks. Configuring your development environment for this kind of thing is outside of the scope of this tutorial, however, I recommend you use Pow if you’re on a Mac.

Add to your Gemfile:

gem 'omniauth-facebook'

Then bundle install.

Step 3: Add your Providers to the App

 Create a new file under config/initializers called omniauth.rb. We’re going to configure our authentication providers through this file.

Paste the following code into the file we created earlier:

In  config/initializers/omniauth.rb

Rails.application.config.middleware.use OmniAuth::Builder do

  provider :facebook, YOUR_APP_ID, YOUR_APP_SECRET

end

Step 4: Creating the Login Page

 rails generate controller sessions new create failure

Step 5: Creating the Authentication Model

rails generate model Authentication provider:string uid:string user_id:integer token:string

 rake db:migrate

 

Add the following code to your app/models/user.rb file:

has_many :authentications validates :name, :email, :presence => true This specifies that a user may have multiple authorizations, and that the name and email fields in the database are required. Next, to your app/models/authentication.rb file, add: belongs_to :user validates :provider, :uid, :presence => true

 

Step 6: Adding a Bit of Logic to our Sessions Controller app/controllers/sessions_controller.rb


def create 

  user = Authentication.from_omniauth(request.env["omniauth.auth"])
      if user
        flash[:notice] = "Authentication successful."
        sign_in(user)
        sign_in_and_redirect(user)
      else
          flash[:notice] = "Authentication Failed."
      end
    end

end



Next, to your app/models/authentication.rb file:-



 def self.from_omniauth(auth)
    authenticate = where(provider: auth['provider'], :uid=>auth['uid']).first_or_initialize
    if authenticate.user
      authenticate.provider = auth.provider
      authenticate.uid = auth.uid
      authenticate.token = auth.credentials.token
    else
          user = User.new
          authenticate.provider = auth.provider
        authenticate.uid = auth.uid
        authenticate.token = auth.credentials.token
        user.email = auth.info.email
        user.password =  Devise.friendly_token.first(8)
        user.save!
        authenticate.user_id = user.id
     end
    authenticate.save
    authenticate.user
  end

In config/routes.rb:-
  get 'auth/:provider/callback', to: 'sessions#create'
 

In Views :- 
  <a href="/auth/facebook" class="auth_provider">       
       Facebook
   </a>