Saturday, December 25, 2004, 5:24:42 AM, Ron Jeffries wrote:
> People generally see that the tenth frame is different: it has two
> small squares, not just one. And when they think about the object
> design for frames, they commonly come up with the idea of a
> polymorphic Frame object, OpenFrame, StrikeFrame, SpareFrame, and
> quite often at least one type of TenthFrame.
> My classes and demonstrations of TDD don't ever go that way. In the
> first C# bowling article on my site, I pushed the design to those
> objects, primarily by forcing the interface. The interface to the
> game actually /tells/ the game whether the next frame is strike,
> spare, open. Cheating, if you ask me. But if the strike or spare
> aren't identified before the frame is created, it's too late to
> choose the right subclass.
Well.... Since you're using Smalltalk this time, that is not
quite a true statement. It's completely possible to start with
an open frame, then have it become a spare, or strike frame,
when it discovers it needs to. I don't think I would have ever
come up with this design approach without your statement
above, and it's a design pattern I discourage, but it might be
really slick in this case. It also shows a capability built
into Smalltalk that just isn't readily available in other
languages.
--
Doug Swartz
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