instance method memoize

# File activesupport/lib/active_support/memoizable.rb, line 44
    def memoize(*symbols)
      symbols.each do |symbol|
        original_method = :"_unmemoized_#{symbol}"
        memoized_ivar = MEMOIZED_IVAR.call(symbol)

        class_eval <<-EOS, __FILE__, __LINE__
          include Freezable

          raise "Already memoized #{symbol}" if method_defined?(:#{original_method})
          alias #{original_method} #{symbol}

          if instance_method(:#{symbol}).arity == 0
            def #{symbol}(reload = false)
              if reload || !defined?(#{memoized_ivar}) || #{memoized_ivar}.empty?
                #{memoized_ivar} = [#{original_method}.freeze]
              end
              #{memoized_ivar}[0]
            end
          else
            def #{symbol}(*args)
              #{memoized_ivar} ||= {} unless frozen?
              reload = args.pop if args.last == true || args.last == :reload

              if defined?(#{memoized_ivar}) && #{memoized_ivar}
                if !reload && #{memoized_ivar}.has_key?(args)
                  #{memoized_ivar}[args]
                elsif #{memoized_ivar}
                  #{memoized_ivar}[args] = #{original_method}(*args).freeze
                end
              else
                #{original_method}(*args)
              end
            end
          end
        EOS
      end
    end