just_time.rb

module DataMapper
  class Property
    class JustTime < Integer
      primitive ::String

      def dump(val)
        case val
          when String
            h,m = val.split(':').map &:to_i
            h % 24 * 60 + m % 60
          else val
        end if val.present?
      end

      def load(val)
        if val.present?
          h = val / 60
          m = val - h * 60
          "#{h}:#{m}"
        end
      end

      def parse(val)
        case val
          when Integer then load(val)
          else val
        end if val.present?
      end

      def typecast_to_primitive(val)
        parse(val)
      end
    end
  end
end