Subj : Re: What the bleep is Coupling? (was: Polymorphism sucks)
To   : comp.programming,comp.object
From : topmind
Date : Thu Jul 07 2005 02:38 pm



Chris Sonnack wrote:
> topmind writes:
>
> >> As A and B are coupled, changes to A require changes to B.
> >>
> >> The more decoupled they are, the less changes ripple thru the system.
> >
> > Okay, but how does polymorphism allegedly
> > avoid this for ALL possible changes?
>
> No one I've heard has alleged this.

Well, I don't know what the heck you are alleging. Even in the
worse-case OO textbook "duplicate case/switch list" scenarios,
a change to case list A does not necessarily "require"
a change to case list B. List B may not care about the
new option. What "required change" linkage is
polymorphism preventing?

Now you may allege that it is most likely that changes
to case list A will result in a change to case list
B, but that is not "requires". That is a statement
of probability. (I may disagree with your probability
value, but that's another issue right now.)

"Requires" is a 100% probability.

(BTW, there is some coupling and change pattern
discussion also happening in the "OOP/OOD Design"
topic.)

-T-

.