I have a function which I have declared:

STDMETHOD(OpenPipe)(/*[in]*/ long swPipe, /*[out, retval]*/ IPipe
**ppIPipe);

Within this function, I want to instantiate a new nested COM object
(to which I can store in a map<int,???> and call functions of the C++
class (which are not exposed COM methods) at a later stage.

How do I get hold of the actual "CAtlObj" C++ object after calling
CoCreateInstance or whatever?

Hi,

Check older posts an read: don't do that!

Its seldom a good idea to rely on the C++ implementation when you are working with
a COM interface pointer as you might only be using a proxy to the real object so a
type cast won't do in all cases.

If you really, really, really must (which I doubt ;-) ) : be sure to only use the
C++ object pointer inproc and avoid marshalling (so make you COM object BOTH as
apartment model). So if your interfaces are directly inherited and implemented
from you c++ class you should be able to type cast back to your C++ class.
To make this hack more clear you could also use COM_INTERFACE_ENTRY_IID(IID_NULL,
CAtlObj) and then call:

CAtlObj* pObj = NULL;
HRESULT hr = QueryInterface(IID_NULL, (void**)&pObj);

BUT the better is to implement a second interface where you put your methods you
would like to call from you code - so you keep it the COM way... What good reason
would there be not to do so?

HTH,
Sven

I assume the object is implemented in the same module that implements
OpenPipe. In this case, don't use CoCreateInstance. Create your object
this way:

CComObject<CPipe>* pPipe;
CComObject<CPipe>::CreateInstance(&pPipe);
// At this point, pPipe is the pointer to raw C++ class
// You can store this pointer somewhere for latter use
// Be aware that the object is created with 0 refcount
// You may want to call AddRef if you don't want the object
// to die on you

// retrieve an interface pointer and return it to the caller
pPipe->QueryInterface(ppIPipe);
// This call implicitly AddRef's

--
With best wishes,
    Igor Tandetnik

"For every complex problem, there is a solution that is simple, neat,
and wrong." H.L. Mencken

Thanks Igor,

Exactly what I needed!