Facebook Connect Integration Using Devise and OmniAuth In Rails App.

Step:1
Add the gems in your gem file

gem ‘devise’
gem 'omniauth'
gem 'omniauth-facebook'

Run the “bundle install” command to install the gem.

Step:2
Define your root url like below

root :to => “home#index”

Step:3
Now you need to run the generator command

rails generate devise:install

This generator will install all Devise configurations.Take a look at them.

Step:4
After done with the above options,you are ready to add Devise to any of your models using the generator:

rails generate devise User

This generator creates a few interesting things: a model file, a migration and a devise_for route.

Step:5
Go the user model “user.rb” and add the following line

devise : omniauthable

Step:6
Run the migrate command to insert the User table in your database.

rake db:migrate

It’ll insert the Users table with some columns.

Step:6
You need two more columns to store provider type and userid given from facebook

rails g migration AddProviderToUsers provider:string uid:string

Runt rake db:migrate to insert the columns in users table.

Step:7
First of all you need to create an app in facebook to get “App-ID” and “App Secret”

https://developers.facebook.com/

Create an app and get the App id and secret key.

Step:8
Now you need to declare the provider name and app id and key.Go to the file config/initializers/devise.rb and the following line

require "omniauth-facebook"
config.omniauth :facebook, "APP_ID", "APP_SECRET"

Step:9
Go to your layout file and the following block


<% if user_signed_in? %>
Signed in as <%= current_user.name %>. Not you?
<%= link_to "Sign out", destroy_user_session_path,:method => :delete %>
<% else %>
<%= link_to "Sign up", new_user_registration_path %> or
<%= link_to "Sign in", new_user_session_path %>
<%= link_to "Sign in with Facebook", user_omniauth_authorize_path(:facebook) %>
<% end %>

When the user clicks on Sign in with Facebook link, they will redirects to the Facebook login page, after entering their credentials it will again redirect the user back to the applications Callback method .

Step:10
Before creating the call back method change your route like below


devise_for :users, :controllers => { : omniauth_callbacks => "omniauth_callbacks" }

Step:11
Create a new controller named as “omniauth_callbacks_controller.rb”.Add the following method in it.


class OmniauthCallbacksController < Devise::OmniauthCallbacksController  
def facebook    
     @user = User.find_for_facebook_oauth(request.env["omniauth.auth"], current_user)     
     if @user.persisted?      
      sign_in_and_redirect @user, :event => :authentication #this will throw if @user is not activated
      set_flash_message(:notice, :success, :kind => "Facebook") if is_navigational_format?
    else
      session["devise.facebook_data"] = request.env["omniauth.auth"]
      redirect_to new_user_registration_url
    end
  end
end

Step:12
Add the following block in your user model.


def self.find_for_facebook_oauth(auth, signed_in_resource=nil)
    user = User.where(:provider => auth.provider, :uid => auth.uid).first
    if user
      return user
    else
      registered_user = User.where(:email => auth.info.email).first
      if registered_user
        return registered_user
      else
        user = User.create(name:auth.extra.raw_info.name,
                            provider:auth.provider,
                            uid:auth.uid,
                            email:auth.info.email,
                            password:Devise.friendly_token[0,20],
                          )
      end    end
  end