Re: Warning

From:

"Alf P. Steinbach" <alfps@start.no>

Newsgroups:

comp.lang.c++

Date:

Wed, 03 Mar 2010 22:48:40 +0100

Message-ID:

<hmmlfq$rqj$1@news.eternal-september.org>

* Leigh Johnston:

"Alf P. Steinbach" <alfps@start.no> wrote in message
news:hmmii4$5jk$1@news.eternal-september.org...

* Leigh Johnston:

"Alf P. Steinbach" <alfps@start.no> wrote in message
news:hmmfnk$i2s$1@news.eternal-september.org...

* Leigh Johnston:

Warning: contact with this newsgroup can result in exposure to
toxic opinions the treatment of which involves the use of copious
amounts of thinking for yourself.

:-)

IMHO you're absolutely right -- but it applies to any newsgroup!

On the other hand, ..., well, wait, I'm not opening that can.

But on the third and gripping hand, while the opinion that I think
triggered that blast, "don't derive from concrete classes", may not
be the world's best advice, it is a practice that works for some
kinds of problems. For example, original COM was built on something
very similar to that idea, "don't expose derivation from concrete
classes to client code". But I think that even that more limited
idea was shown to be too drastic, when COM+ did away with it. :-)

COM does not mandate that policy;

Well, you then continue saying that it does:

it says nothing on how a particular server class is implemented, i.e.
a server class could be implemented by a number of classes related
through inheritance. All that is exposed to the client is the
abstract interface (a collection of public pure virtual functions).

So, that's a self-contradiction.

Which means that readers must think for themselves.

You said original COM has built on the idea that you don't derive from
concrete classes and I was contradicting that: you can have a class
hierarchy that implements a particular COM interface, i.e. there doesn't
need to be a one-to-one mapping between a COM interface and a single

Yes, except for lack of attention to detail you're violently agreeing with me. :-)

Note what you quoted. It's not the same as your paraphrase.

Cheers,

- Alf