Re: Internal COM objects using CComObject possible ?

"Jeremy Boschen" <jboschen[at]mutexed[dot]com>
Fri, 15 Dec 2006 12:08:40 -0500
The general pattern goes down like this...

#include <myclass.h>
CComObject<CMyClass>* pMyClass;
IDispatch* pDisp;

If you look at the ATL source for the various CComObject<> variants and
IClassFactory implementations it may start to make more sense. The
registration pieces of COM get any other client to your module's
CreateInstance() methods. What you want to do is skip the pieces that get
you that far via COM runtime, and start from there.

The one important thing to note about the ATL CreateInstance() methods is
that they _do_not_ add an initial reference count on the object they
instantiate which is why you must immediately add one when the call returns
successfully. It's also important to note that the CComObject<CMyClass>* is
_not_ an interface pointer, it's a C++ class object, so you can setup member
variables, etc, but anything you use beyond that point (eg IDispatch) should
be acquired via QueryInterface().

- Jeremy Boschen

"Xavier Roche" <> wrote in message

Hi folks,

I need to instantiate an internal COM object with IDispatch support (using
IDispatchImpl wrappers), but without any registration procedures (I don't
want to write anything in the registry - the object is created internally
and passed to other objects)

The idl file is compiled, and the TLB is merged in the module, but no
registration procedure is ever processed anywhere (and I don't want to).

When calling CMyClass::CreateInstance(&pClass), I always get a COM error
saying that the module wasn't found.. I guess that the Type Library and
other details have to be fetched in some default FinalConstruct (the
constructor is being called, but the classe is destroyed after that),
which fails because no classes were registered.

[ Of course I can't just do a CMyClass *c = new CMyClass() as the class is
abstract and misses all template code ]

What do I need to override so that this can be achieved without (too much)
pain ? Is it possible or am I doomed ?

My class looks like:

class CMyClass :
public CComObjectRoot,
public CComCoClass<CMyClass ,&CLSID_MyClass >,
public IDispatchImpl<CMyClass, &IID_IMyClass, &LIBID_myClassLib>



Any hint would be really welcome.

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