User.rb

class User < ActiveRecord::Base
  # Include default devise modules. Others available are:
  # :token_authenticatable, :confirmable,
  # :lockable, :timeoutable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable,
         :omniauthable
         
  def full_name
    ([first_name, last_name] - ['']).compact.join(' ')
  end
  
  def self.from_omniauth(auth)
    where(auth.slice(:provider, :uid)).first_or_create do |user|
      user.provider = auth["provider"]
      user.uid = auth["uid"]
      user.username = auth["info"]["nickname"]
    end
  end
  
  def self.new_with_session(params, session)
    if session["devise.user_attributes"]
      new(session["devise.user_attributes"]) do |user|
        user.attributes = params
        user.valid?
      end
    else
      super
    end    
  end
  
  def password_required?
    super && provider.blank?
  end
  
  def update_with_password(params, *options)
    if encrypted_password.blank?
      update_attributes(params, *options)
    else
      super
    end
  end
end