activemodel validation , except and only options

lib/active_model/credit_card_number_validator.rb

@@ -13,13 +13,28 @@ module Validations
     class CreditCardNumberValidator < EachValidator
 
       def validate_each(record, attribute, value)
-        brands = options.fetch(:brands, :any)
-        record.errors.add(attribute) unless credit_card_valid?(value, brands == :any ? [] : Array.wrap(brands))
+        record.errors.add(attribute) unless credit_card_valid?(value, extract_brands(options))
       end
 
       def credit_card_valid?(number, brands = [])
         CreditCardValidations::Detector.new(number).valid?(*brands)
       end
+
+      protected
+
+      def extract_brands(options)
+         if options.has_key?(:brands)
+           options[:brands] == :any ? [] : Array(options[:brands])
+         elsif options.has_key?(:only)
+           Array(options[:only])
+         elsif options.has_key?(:except)
+           Array(CreditCardValidations::Detector.brands.keys) - Array(options[:except])
+         else
+           []
+         end
+
+      end
+
     end
   end
 end