Re: Problem with multiple inheritance

From:

"AliR $VC++ MVP$" <AliR@online.nospam>

Newsgroups:

microsoft.public.vc.mfc

Date:

Tue, 24 Feb 2009 10:03:13 -0600

Message-ID:

<UTUol.17634$yr3.12379@nlpi068.nbdc.sbc.com>

Things don't quite add up.

If InheritFromC is only in AB and ABC then how can you call it on a A *
object in your MyFunction without any casts?

Have you tried dynamic type casting? That might eliminate your problem.
(you have to turn on the RTTI compiler settings)

void MyFunction(A *myObject)
{
    C *mySecondObject = dynamic_cast<C*>(myObject);

    if (myObject != NULL)
    {
        mySecondObject->I_Am_From_C();
    }
}

AliR.

"No_Name" <no_mail@no_mail.com> wrote in message
news:go14f3$h38$1@aioe.org...

Hello,

I work on an application with multiple inheritance. I work with Visual C++
2005 & Windows CE.

I have a class named A.

I have a class named AB which inherits from A.

I have a class named C.
Class C has a function I_Am_From_C().

I have a class named ABC which inherits from AB and from C.

Class AB has a function InheritsFromC() which gives false;
Class ABC has a function InheritsFromC() which gives true;

I am trying to write generic C++ code to be able to deal with my classes.

In my code, O is an object coming from another function. It can be an AB
or an ABC object.
I write the following :

void MyFunction(A *myObject)
{
  C *mySecondObject;

  if (myObject->InheritsFromC() == true)
   {
    mySecondObject = (C *)myObject;
    mySecondObject->I_Am_From_C();
   }

}

but when I make this code run, the calling of the I_Am_From_C() function
crashes, and in debug I can see that the C object named mySecondObject is
not correctly initialized (all his parameters have random values).

Isn't it a good way to manage myObject when it inherits from C ? Can you
help me with a better way to be able to call the I_Am_From_C() function
from myObject where it effectively inherits from C ?

Thank you very much !