Re: Inheritance versus Composition
<printdude1968@gmail.com> wrote in message
news:1173967479.248857.93180@y66g2000hsf.googlegroups.com...
On Mar 15, 9:10 am, Eric Sosman <esos...@acm-dot-org.invalid> wrote:
I suspect I may have offended you, which was not my intent.
If I have done so, I ask your forgiveness.
The reason I think your question makes no sense is that it
asks "which is better" but doesn't say anything about "for what
purpose?" Mitosis is not "better than" meiosis; they are
different (although related) processes with different functions.
If you want to make red blood cells mitosis is better than
meiosis; if you want to make eggs it's the other way around.
Similarly with inheritance and composition: They are related
(both are ways of deriving a more specialized construct from a
more general substrate), but they are different and serve different
purposes. Neither is "better" than the other in isolation, not
until the purpose enters the picture.
Which is better, a bicycle or a banana? It depends on whether
your purpose is to get from Here to There, or from Hungry to Fed.
Remind me not to respond to posts before my first cup of coffee in the
morning. If composition is more desirable than inheritance, then why
do the books I have teach inheritance first? Wouldn't it be better
for them to talk about composition first?
The whole point of Eric's message was to point out that composition is
NOT more desirable than interface. They do two different things, and are
useful in different situations. The advice "favor composition over
inheritance" is saying for the situations where both solutions are equally
applicable, choose composition. But there are situations where inheritance
is a much better fit than composition, and there are situations where
composition is a much better fit than inheritance.
- Oliver