title: Undefined method add_to_base
body: <p>I'm working with activemerchant and it raise me this error when validating the card is this ok in rails 3? thank you in advance more power to all</p>
  
  <pre><code>belongs_to :reservation
  
    attr_accessor :card_number, :card_verification
  
    validate :validate_card, :on =&gt; :create
  
    def validate_card
      unless credit_card.valid?
        credit_card.errors.full_messages.each do |message|
          errors.add_to_base "error"
        end
      end
    end
  
      def credit_card
      @credit_card ||= ActiveMerchant::Billing::CreditCard.new(
        :type               =&gt; card_type,
        :number             =&gt; card_number,
        :verification_value =&gt; card_verification,
        :month              =&gt; card_expires_on.month,
        :year               =&gt; card_expires_on.year,
        :first_name         =&gt; first_name,
        :last_name          =&gt; last_name
      )
    end
  </code></pre>
  
  <p>it is pointing to <code>Undefined method add_to_base</code> </p>