I've searched Deja for information regarding this but didn't find any
info specific to my problem.

The problem is that I am serializing a CArray of pointers to CObject
derived objects and Things Don't Work.

What sets this particular issue apart from others that I have read about
in the group archives, various FAQ's and the MFC documentation is that
my object array is defined like this:

CArray<CFruit*, CFruit*> BagOfFruit;

and that CFruit is an abstract base class derived from CObject. The
members of BagOfFruit point to things such as CBanana, CApple or
CKiwiFruit, which are all derived from CFruit.

However, if I put the DECLARE_SERIAL and IMPLEMENT_SERIAL macros in
their proper places in CFruit's class definition and implementation
files, things go decidedly pear-shaped, so to speak. The compiler
complains like this:
error C2259: 'CFruit' : cannot instantiate abstract class due to
following members:
warning C4259: 'class CFruit *CFruit::Clone(void)' : pure virtual
function was not defined
warning C4259: 'void CFruit::Draw(class CDC*, bool)' : pure virtual
function was not defined

The problem is that being an abstract base class is a requirement by
design for CFruit. A CFruit object should not exist.

If I comment out these macros in CFruit the compiler complains about the
?_SERIAL macros in CApple, CBanana, etc, saying:
error C2039: 'classCFruit' : is not a member of 'CFruit'
error C2065: 'classCFruit' : undeclared identifier

All of my objects have the correct Serialize(CArchive& ar) functionality
and I've written a SerializeElements functions for BagOfFruit.

Has anyone got any ideas of what's my problem?

Thankyou,
Rodney Lorrimar

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I had a quick look at this .. the problem is your macros. Have you looked to
see what these macros do ?

XXX_DYNAMIC allows RunTime information

XXX_DYNCREATE does XXX_DYNAMIC and allows dynamic creation through
CreateObject

XXX_SERIAL DOES xxx_DYNCREATE and overloads the << and >> operators

you declare your CFruit to be XXX_SERIAL so the compiler generates
XXX_SERIAL is a superset of XXX_DYNCREATE
so what does IMPLEMENT_DYNCREATE do ?

#define IMPLEMENT_DYNCREATE(class_name, base_class_name) \
 CObject* Pascal class_name::CreateObject() \
  { return new class_name; } \

Wow, your compiler has generated

CFruit *PASCAL CFruit::CreateObject()
{ return new CFruit; }

No can do ... CFruit is a virtual base class.

How do you get around this ? Well a quick ( but very educated ) guess

DECLARE_DYNAMIC / IMPLEMENT_DYNAMIC   your CFruit class - that gets rid of
the 'new CFruit' code generation but allows RTTI. Then with your derived
classes CApple, CBanana etc. You need to DECLARE_SERIAL / IMPLEMENT_SERIAL.

Hope it works.

Thankyou Robert for your reply.

I had a little look at the definitions and even tried putting
XXX_DYNCREATE into CFruit. However, I had little idea of what I was
doing so my uneducated guesses were ignored and I looked for other
things that could be the problem.

When I put XXX_DYNAMIC into CFruit it compiled fine. As an added bonus,
I made a closer examination of the macros and worked out what they
actually do. :)

Now to work out how to make those serialized pointers behave...

Rodney Lorrimar

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Before you buy.