OmniAuth with Twitter

devise.rb

config.omniauth :facebook, FACEBOOK_APP_ID, FACEBOOK_APP_SECRET, { :scope => 'user_status,publish_stream' }
config.omniauth :twitter, TWITTER_KEY, TWITTER_SECRET

login.html

= link_to "Sign in with Twitter", omniauth_authorize_path(:user, :twitter)

omniauth_callbacks_controller.rb

module Users
  class OmniauthCallbacksController < Devise::OmniauthCallbacksController
    def facebook
      oauthorize
    end

    def twitter
      oauthorize
    end

    private

    def oauthorize
      @user = User.find_from_oauth_attrs(oauth_attrs)

      if @user.persisted?
        flash[:notice] = I18n.t "devise.omniauth_callbacks.success", :kind => "Facebook"
        sign_in_and_redirect @user, :event => :authentication
      else
        if current_user
          authorization = current_user.authorizations.build(:uid => oauth_attrs[:uid],
                                                            :provider => oauth_attrs[:provider],
                                                            :token => oauth_attrs[:token],
                                                            :secret => oauth_attrs[:secret])
          if authorization.save
            flash[:notice] = "#{authorization.provider.capitalize} authorization has been added"
          end

          redirect_to edit_user_registration_path(current_user)
        else
          session["devise.oauth_attrs"] = oauth_attrs
          redirect_to new_user_registration_url
        end
      end
    end

    def oauth_attrs
      data = request.env['omniauth.auth']
      { :provider => data.provider,
        :uid => data.uid,
        :email => data.info.email,
        :first_name => data.info.first_name,
        :last_name => data.info.last_name,
        :token => data.credentials.token,
        :secret => data.credentials.secret }
    end
  end
end

routes.rb

 devise_for :users, :controllers => { :omniauth_callbacks => "users/omniauth_callbacks",
                                       :registrations => "registrations" }
  devise_scope :user do
    delete '/users/:id/authorization/:auth_id' => "registrations#destroy_authorization", :as => :destroy_authorization
    resource :profile, only: [:show]
  end