class ActiveModel::Validations::FormatValidator

def validate_each(record, attribute, value)
  if options[:with] && value.to_s !~ options[:with]
    record.errors.add(attribute, :invalid, options.except(:with).merge!(:value => value))
  elsif options[:without] && value.to_s =~ options[:without]
    record.errors.add(attribute, :invalid, options.except(:without).merge!(:value => value))
  end
end