🚀 go-pugleaf

Hi all,

I face a problem related to C++ classes. And I would like to know how to
get rid of it.

I defined 2 classes that know each others lets call the A1 and B1.
A1 has a slot (bb) that contains a B1
B1 has a slot (aa) that contains an A1.

Up to now, everythings fine. Now, I would like to expend the
functionality of the classes by sub-classing A1 and B1.

A2 inherits from A1.
A2 has one more method (DoThis) that wasn't defined in A1
The aa slot of an A2 instance always contains a B2 instance.

B2 inherits from B1
B2 has one more method (Dothat) that wasn't defined in B1
The aa slot of an A2 instance always contains a B2 instance.

in A2::Dothis(), I call the method DoThat for the B2 that is in the bb
slot:
void A2::DoThis(void) { (this->bb)->DoThat(); }

This works only if I cast (this->bb) to a B2*. If I don't, my codewarrior
tells me:
Error   : 'DoThat' is not a struct/union/class member
A2.cp line xx   (this->bb)->DoThat();

Hence I have to write:
void A2::DoThis(void) { ((B2 *)(this->bb))->DoThat(); }

But now, I want to introduce new classes that behave slightly differently
than B2.

B3 inherits from B2 and redefines DoThat().

A2 is not modified (but its bb slot contains a B3 instance).

When I call A2::DoThis(), B2::DoThat() is called because of the casting.
And I would like B3::DoThat() to be called instead.

How can I do this ? Am I missing something in C++ hierarchies principles ?

Thanks in advance,

Gilles Serasset,

======================================================
 Au paradis, on est assis a la droite de Dieu.
 C'est normal, c'est la place du mort.    P. Desproges
-----  Gilles.Serasset@imag.fr (Gilles Serasset)  ----
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