Re: C++ polymorphism question

From:

Barry <dhb2000@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Wed, 19 Sep 2007 20:42:08 +0800

Message-ID:

<fcr5gk$snv$1@aioe.org>

Gianni Mariani wrote:

Jonas Huckestein wrote:

Hi there,

I was wondering, whether I
can access members of a
derived class from within
it, if I accessed it from a
virtual function on the base
classpointer ^^ Example:

class A {
virtual void oskar(void);
};

class B : A {
void emil(){};

the ';' not needed

void oskar(void)
{emil();};};

the ';' after the function is not needed ... don't put it at the end of
functions.

not "not needed", but even wrong, but I'm sure the standard allow extra
';' in class definition or not; AFAIK, some library like /CppUnit/ even
borrows some technique to avoid "extra ';' error" for some compilers,
what compile(s)? I don't know.

A* peter = new B;
B->oskar();

Is this allowed? I know it
is not possible to call emil
directly, but thiswould be a
fine workaround.

This is allowed. Not only is it allowed, it is the intention for

the code is even illformed

if /A/ makes /oskar/ public and /B/ uses public inheritance
then we can write
peter->oskar();

I think this is the OP's intent

virtual functions to have access to the class it is defined in.

Don't call it from "A"'s constructor though, you'll get surprises.

--
Thanks
Barry