Python Design Patterns - composition vs. inheritance

Neil Cerutti horpner at yahoo.com
Sat Nov 17 16:57:14 CET 2007


On 2007-11-17, Odalrick <odalrick at hotmail.com> wrote:
>> But that breaks expectations: a user doesn't expect
>> set_width() to affect the height.
>
> I can't speak for everyone but I certainly expect setting the
> width of a Square to change it's height. In fact, that would
> probably be the reason I used a Square rather than a Rectangle
> in the first place.

Some of the dissonance is from assuming that rectangles can
mutate themselves. I've never seen one do that! ;) The rest of
the dissonance is caused by strong typing. A rectangle with equal
width and height is still a rectangle, in a strongly typed
language.

-- 
Neil cerutti



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