Modify your Gemfile to include the Devise gem:

gem 'devise'

Then update your gems with:

$ bundle install

Run the installers in your project:

$ rails generate devise:install

Then create your Devise model (e.g. User) with:

$ rails generate devise User

you'll need to set up the default URL options for the Devise mailer in environment.rb file config/environments/development.rb:

config.action_mailer.default_url_options = { host: 'localhost', port: 3000 }

Devise makes some changes to your database, so you'll need to run the created migrations:

$ rake db:migrate

class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController
  include OmniConcern
  %w[facebook twitter gplus linkedin].each do |meth|
    define_method(meth) do
      create
    end
  end
end

Note: In the part “%w[facebook twitter gplus linkedin]”, you should list all the social accounts you will use.

module OmniConcern
  extend ActiveSupport::Concern
  def create
    auth_params = request.env["omniauth.auth"]
    provider = AuthenticationProvider.get_provider_name(auth_params.try(:provider)).first
    authentication = provider.user_authentications.where(uid: auth_params.uid).first
    existing_user = User.where('email = ?', auth_params['info']['email']).try(:first)
    if user_signed_in?
      SocialAccount.get_provider_account(current_user.id,provider.id).first_or_create(user_id: current_user.id ,  authentication_provider_id: provider.id , token: auth_params.try(:[],"credentials").try(:[],"token") , secret: auth_params.try(:[],"credentials").try(:[],"secret"))
      redirect_to new_user_registration_url
    elsif authentication
      create_authentication_and_sign_in(auth_params, existing_user, provider)
    else
      create_user_and_authentication_and_sign_in(auth_params, provider)
    end
  end
  def sign_in_with_existing_authentication(authentication)
    sign_in_and_redirect(:user, authentication.user)
  end
  def create_authentication_and_sign_in(auth_params, user, provider)
    UserAuthentication.create_from_omniauth(auth_params, user, provider)
    sign_in_and_redirect(:user, user) 
  end
  def create_user_and_authentication_and_sign_in(auth_params, provider)
    user = User.create_from_omniauth(auth_params)
    if user.valid?
        create_authentication_and_sign_in(auth_params, user, provider)
    else
        flash[:error] = user.errors.full_messages.first
        redirect_to new_user_registration_url
    end
 end
end

class CreateAuthenticationProviders < ActiveRecord::Migration
    def change
        create_table "authentication_providers", :force => true do |t|
            t.string   "name"
            t.datetime "created_at",                 :null => false
            t.datetime "updated_at",                 :null => false
        end
        add_index "authentication_providers", ["name"], :name => "index_name_on_authentication_providers"
        AuthenticationProvider.create(name: 'facebook')
        AuthenticationProvider.create(name: 'twitter')
        AuthenticationProvider.create(name: 'gplus')
        AuthenticationProvider.create(name: 'linkedin')
    end
end

class CreateUserAuthentications < ActiveRecord::Migration
    def change
        create_table "user_authentications", :force => true do |t|
            t.integer  "user_id"
            t.integer  "authentication_provider_id"
            t.string   "uid"
            t.string   "token"
            t.datetime "token_expires_at"
            t.text     "params"
            t.datetime "created_at",                 :null => false
            t.datetime "updated_at",                 :null => false
        end
        add_index "user_authentications", ["authentication_provider_id"], :name => "index_user_authentications_on_authentication_provider_id"
        add_index "user_authentications", ["user_id"], :name => "index_user_authentications_on_user_id"
    end
end

has_many :users
has_many :user_authentications

belongs_to :user
belongs_to :authentication_provider

serialize :params

def self.create_from_omniauth(params, user, provider)
    token_expires_at = params['credentials']['expires_at'] ? Time.at(params['credentials']['expires_at']).to_datetime : nil
    create(
            user: user,
            authentication_provider: provider,
            uid: params['uid'],
            token: params['credentials']['token'],
            token_expires_at: token_expires_at,
            params: params,
          )
end

include OmniauthAttributesConcern

has_many :user_authentications

devise :omniauthable, :database_authenticatable, :registerable,:recoverable, :rememberable, :trackable

def self.create_from_omniauth(params)
    self.send(params.provider,params)
end

module OmniauthAttributesConcern
    extend ActiveSupport::Concern
    module ClassMethods
        Add Methods here 
    end
end

In this concern we can create methods for each social media to fetch and store attributes.

def twitter params
  (params['info']['email'] = "dummy#{SecureRandom.hex(10)}@dummy.com") if params['info']['email'].blank?
  attributes = {
                 email: params['info']['email'],
                 first_name: params['info']['name'].split(' ').first,
                 last_name: params['info']['name'].split(' ').last,
                 username: params['info']['nickname'],
                 password: Devise.friendly_token
               }
  create(attributes)
end

Note: Twitter only returns an email address if the user has confirmed his/her email at Twitter; otherwise the nil value is returned.

• We can add other social media accounts the same way we have added Twitter above.

• The profile image from the social media account can also be fetched, and will be passed as

  remote_image_url: params['info']['image']
  

  Note: the above example is meant for the CarrierWave gem, and 'image' in remote_image_url is the DB column. You can use any other gem and pass params['info']['image'] to it.

devise_for :users, controllers: {omniauth_callbacks: 'users/omniauth_callbacks'}

For Facebook

config.omniauth :facebook, facebook_app_id, facebook_secret_key, :display => "popup", :scope => 'email,publish_actions', info_fields: 'email,name'

For Twitter

config.omniauth :twitter, twitter_app_id, twitter_secret_key, :display => "popup", :scope => 'email'

For Linkedin

config.omniauth :linkedin, linkedin_app_id, linkedin_secret_key, :display => "popup", :scope => 'r_emailaddress,r_basicprofile'

For Google+

config.omniauth :gplus, gplus_app_id, gplus_secret_key, :display => "popup", scope: 'userinfo.email, userinfo.profile'

Note: the display: "popup" attribute is used when we want social media signup to open in a separate browser window.

gem 'omniauth-oauth2' , '~> 1.3.1'
gem 'omniauth'
gem 'omniauth-facebook'
gem 'omniauth-twitter'
gem 'omniauth-gplus'
gem 'omniauth-linkedin'

Run the bundle install command, restart your server and off you go!