#MODEL
#models/reservations/booking.rb
module Reservations

  # Klasa reprezentująca rezerwacje.
  class Booking < ActiveRecord::Base
    set_table_name 'reservations_bookings'

    include Reservations::Validations

    attr_accessible :hotel_id, :start_date, :end_date, :currency,
                    :first_name, :last_name, :email, :phone_number, :special_requests,
                    :cc_type, :cc_number, :cc_first_name, :cc_last_name, :cc_expiration_date, :cc_cvc,
                    :existing_bookings_rooms_attrs, :total_rake, :payed_rake,
                    :addr_street_name, :addr_house_number, :addr_flat_number,
                    :addr_postal_code, :addr_city, :addr_country, :full_guest_name, :room_id


    # Properties
    acts_as_paranoid

    has_friendly_id :token, :approximate_ascii => true

  end
end

#MODUL
#models/reservations/booking_modules/validations.rb

require 'active_support/concern'

module Reservations
    module Validations
      extend ActiveSupport::Concern

      included do
        validates :token, :uniqueness => true, :presence => true

        validates :hotel_id, :currency, :start_date, :end_date, :presence => true
        validate :validate_rooms

        validates_date :start_date, :on_or_after => Date.today
        validates_date :end_date, :after => :start_date


        validates :first_name, :last_name, :presence => true, :unless => :fresh?
        validates :email, :email => true, :presence => true, :confirmation => true, :unless => :fresh?


        validates :total_rake, :payed_rake, :guarantee_rake, :cancel_rake, :presence => true
        validates_associated :credit_card, :unless => :has_credit_card?

        def validate_rooms
          if self.has_rooms?
            return true
          else
            self.errors.add(:rooms, I18n.t('booking.error.no_room_chosen'))
            return false
          end
        end

      end

    end

end

#ERROR

uninitialized constant Reservations::Validations (NameError)