append_features

# File lib/rss/syndication.rb, line 18
    def self.append_features(klass)
      super

      klass.install_must_call_validator(SY_PREFIX, SY_URI)
      klass.module_eval do
        [
          ["updatePeriod"],
          ["updateFrequency", :positive_integer]
        ].each do |name, type|
          install_text_element(name, SY_URI, "?",
                               "#{SY_PREFIX}_#{name}", type,
                               "#{SY_PREFIX}:#{name}")
        end

        %(updateBase).each do |name|
          install_date_element(name, SY_URI, "?",
                               "#{SY_PREFIX}_#{name}", 'w3cdtf',
                               "#{SY_PREFIX}:#{name}")
        end
      end

      klass.module_eval(        alias_method(:_sy_updatePeriod=, :sy_updatePeriod=)        def sy_updatePeriod=(new_value)          new_value = new_value.strip          validate_sy_updatePeriod(new_value) if @do_validate          self._sy_updatePeriod = new_value        end, __FILE__, __LINE__ + 1)
    end