> I'm trying to create a COM object with VC++6 and ATL for my company.
> From now, I'm just doing tests to understand better how this works
> So I write an ATL object with VC++ and I test it under VB6.
> Using the class view, I can add simple properties to my object, by
> simple, I mean properties of a predefined type like long, short...
> Now I created a second object which has its own interface. This gives
> me that
> CObj1 et IObj1, CObj2 et IObj2
> Theses are the names given by VC++. In the registry, and so far for
> VB, I have  Obj1 and Obj2
> I would like Obj1 to contain a reference to an object of type Obj2
> that I could call this way from VB :
> AnObj1Instance.APropertyOfTypeObj2.AMethodFromObj2

> So I added the follozing lines to the IDL file in my project :

> [propget, id(4)] HRESULT APropertyOfTypeObj2([out, retval] IObj2
> **pVal);
> [propput, id(4)] HRESULT APropertyOfTypeObj2([in] IObj2 *newVal);

> And I wrote the following functions to access the property

> STDMETHODIMP CSGraphic::get_APropertyOfTypeObj2(IObj2 **pVal)
> {
>         *pVal = APointerOfTypeIObj2;
>         return S_OK;
> }

> STDMETHODIMP CSGraphic::put_APropertyOfTypeObj2(IObj2 *newVal)
> {
>         APointerOfTypeIObj2 = newVal;
>         return S_OK;
> }

> With APointerOfTypeObj2 declared this way :
> IObj2 * APointerOfTypeObj2;

> This pointer is initialized in the CObj1 constructor in this way :

> HRESULT hr = CoCreateInstance(CLSID_Obj2, NULL, CLSCTX_ALL, IID_IObj2,
> (void **)&APointerOfTypeIObj2);

> And in the destructor I do this :
> APointerOfTypeIObj2->Release();

> Now, the Obj2 interface (IObj2) proposes a method (ding) and a long
> property (thing)
> In VB, I can create instances of Obj2 without any problems and I
> access the method and the property without any problem.

> Now, If I create an Obj1 and I access any other property than
> APropertyOfTypeObj2, everything is ok until the object is destroyed :
> VB crashes and if I ask a debug by clicking cancel, I go to the source
> of my object on the line where Release is called.
> So I decided to suppress this call, even if I think I must keep it.
> And after deleting this call I got no more problems in VB.
> Well, no more problems with this !
> Actually I then tried to access APropertyOfTypeObj2. If i do this :
> AnInstanceOfObj1.APropertyOfTypeObj2.ding

> Everything is ok and the code in ding (a simple beep) works well.
> But as soon as I want to do this
> AnInstanceOfObj1.APropertyOfTypeObj2.thing = 2

> Or even reading the value of thing,
> I got a big error with the message Memory could not be read... and if
> I ask for a debug, I got a disassembled version of the DLL...

> The strangest thing is that if create an Obj2, accessing the thing
> property doesn't create the error.
> So I think I made a big error in the way I include Obj2 in Obj1 but I
> dont't see what.
> I'm searching on the net and the forums but I did'nt find anything
> yet.
> Thanks in advance for your help