Re: Interfaces in C++
On Oct 10, 11:09 am, anon <a...@no.invalid> wrote:
Pete Becker wrote:
On 2008-10-07 02:07:33 -0400, anon <a...@no.invalid> said:
Maik wrote:
On 6 Okt., 21:12, "A.Gallus" <u...@rz.uni-karlsruhe.de> wrote:
Bingo, that did the job, thx!
class A
{
virtual void myfunc() = 0;
};
class B : public A
{
You should consider to prefer
class B : public virtual A
to avoid being bitten by:
http://www.parashift.com/c++-faq-lite/multiple-inheritance.html#faq-25=
..8
which will most likely happen if one uses the interface pattern.
I think that is worse performance wise then just this:
class B : public A
At least thats what I read here:
http://www.agner.org/optimize/#optimize
And int is faster than double, so I won't use
floating-point. Unfortunately, that often gives the wrong
answer.
What I suggested is "do not use it, unless you have to"
We're talking here about a very general case of an interface
which extends another interface. The correct "default" is to
use virtual inheritance, since it is always "correct"; with
non-virtual inheritance, you artificially restrict the ways the
client code can use the interface.
Seriously: virtual and non-virtual inheritance have rather
different meanings, and performance concerns (whether real
or imaginary) never overrule correct semantics.
http://en.wikipedia.org/wiki/Virtual_inheritanceexplains my
understanding of the virtual inheritance.
You haven't said what are differences in virtual and
non-virtual inheritance meanings.
He probably supposed that that was known.
Whether I am going to use a virtual inheritance depends on the
design, and I would not suggest to people to use it because it
might prevent a bug.
Certainly, it depends on the design. If I'm inheriting a
concrete implementation class directly from a single interface,
and the concrete implementation class is not designed to serve
further as a base class, then I don't bother with virtual
inheritance. If I'm extending an interface (in the sense that
Java uses the word "extends"), then I do, systematically. If
I'm providing a concrete implementation class which uses the
template method pattern to allow for further client
customization, it depends, but virtual inheritance has the
advantage of allowing more flexibility to the client.
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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