User auth key

console

$ rails c
Loading development environment (Rails 4.1.6)
2.1.4 :001 > User.create(email: "stefan@gmail.com", password: "somepassword123", password_confirmation: "somepassword123")
   (0.2ms)  begin transaction
  User Exists (0.3ms)  SELECT  1 AS one FROM "users"  WHERE "users"."auth_token" = '' LIMIT 1
  User Exists (0.1ms)  SELECT  1 AS one FROM "users"  WHERE "users"."email" = 'stefan@gmail.com' LIMIT 1
   (0.1ms)  rollback transaction
 => #<User id: nil, email: "stefan@gmail.com", encrypted_password: "$2a$10$l6LMCC4/LbAZQUxQBZK04O9ks3WXswUNfzhAQpMwBGe...", reset_password_token: nil, reset_password_sent_at: nil, remember_created_at: nil, sign_in_count: 0, current_sign_in_at: nil, last_sign_in_at: nil, current_sign_in_ip: nil, last_sign_in_ip: nil, created_at: nil, updated_at: nil, auth_token: ""> 
2.1.4 :002 > 

user

class User < ActiveRecord::Base
  validates :auth_token, uniqueness: true
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,
  :recoverable, :rememberable, :trackable, :validatable

  before_create :generate_authentication_token!

  has_many :products, dependent: :destroy

  def generate_authentication_token!
    begin
      self.auth_token = Devise.friendly_token
    end while self.class.exists?(auth_token: auth_token)
  end

end

Problem was the validation because i have already created a User before adding the auth_token, so a empty auth token was already in the db. Of course that the before_create method is called before save the User is set up with the default value "" => the rollback is made before the before_create method is called.