custom user class to store user attributes retrieved from omniauth

application_controller.rb

class ApplicationController < ActionController::Base
  protect_from_forgery
  before_filter :login_required
  helper_method :current_user

  def current_ability
    @current_ability ||= Ability.new(current_user)
  end

  protected

  def login_required
    if !current_user
      respond_to do |format|
        format.html  {
          redirect_to '/auth/identity'
        }
        format.json {
          render :json => { 'error' => 'Access Denied' }.to_json
        }
      end
    end
  end

  def current_user
    session[:user]
  end

  rescue_from CanCan::AccessDenied do |exception|
    flash[:alert] = "Access Denied!"
    redirect_to "#{CUSTOM_PROVIDER_URL}"
  end

end

user.rb

class User

  ATTRIBUTES = [:uid, :membername, :email, 
                :role, :id, :contact_number, :menubuilder, :venue, :venue_id]

  attr_accessor *ATTRIBUTES

  def initialize(attributes = {})
    self.attributes = attributes
  end

  def self.from_omniauth(omniauth)
    User.new(omniauth['info']).tap do | user |
      user.uid = omniauth['uid']
    end
  end

  def attributes
    ATTRIBUTES.inject(ActiveSupport::HashWithIndifferentAccess.new) do |result, key|
      result[key] = read_attribute_for_validation(key)
      result
    end
  end

  def attributes=(attrs)
    attrs.each_pair {|k, v| send("#{k}=", v) if respond_to?("#{k}=") }
  end

  def read_attribute_for_validation(key)
    send(key)
  end

end

user_session_controller.rb

class UserSessionsController < ApplicationController
  before_filter :login_required, :only => :destroy

  respond_to :html

  # Omniauth callback method
  def create
    session[:user] = User.from_omniauth(request.env['omniauth.auth'])

    flash[:notice] = "Successfully logged in"
    redirect_to root_path
  end

  # Omniauth failure callback
  def failure
    flash[:notice] = params[:message]
    redirect_to root_path
  end

  # logout - Clear our rack session BUT essentially redirect to the provider
  # to clean up the Devise session from there too !
  def destroy
    session[:user] = nil

    flash[:notice] = 'You have successfully signed out!'
    redirect_to "#{CUSTOM_PROVIDER_URL}/logout"
  end
end