C++ – ATL COM Server – creating COM object defined in ATL Server from this server

Just a suggestion - if your COM object does not need to do anything special with COM related stuff then you can implement code such that the real logic that your base COM class does is encapsulated in another plain old C++ class say CBaseLogic.

CBaseLogic : IBase

class ATL_NO_VTABLE CBase :
    public CComObjectRootEx<CComSingleThreadModel>,
    public CComCoClass<CBase, &CLSID_Base>,
    public ISupportErrorInfo,
    public IConnectionPointContainerImpl<CBase>,
    public CProxy_IBaseEvents<CBase>,
    public IDispatchImpl<IBase, &IID_IBase, &LIBID_ExampleLib
{
CBaseLogic m_LogicObj; /* Method calls are simply forwarded to this member */
};


CDerivedLogic : public CBaseLogic

class ATL_NO_VTABLE CDerived :
    public CComObjectRootEx<CComSingleThreadModel>,
    public CComCoClass<CDerived, &CLSID_Base>,
    public ISupportErrorInfo,
    public IConnectionPointContainerImpl<CDerived>,
    public CProxy_IBaseEvents<CDerived>,
    public IDispatchImpl<IBase, &IID_IBase, &LIBID_ExampleLib
{
CDerivedLogic m_LogicObj;
};

This achieves what you are trying to do with the added advantage of

1. Keeps your real program logic separate from the infrastructure / packaging (COM)
2. Makes the real logic platform independent.
3. Future maintainer need not understand your clever COM hack
4. Keeps your program logic clean and away from the COM syntax, improving readability
5. Makes re-use of real logic easier in other forms of packaging eg as a C DLL

I never found out why the wizard determined that the object name existed already - I'm guessing something was cached somewhere that I couldn't track down.

In the end, I appended a 2 to the end of the interface name when creating it which allowed it to be added. Then I replaced all the occurrences of IXxxInterfaceName2 with IXxxInterfaceName. Everything worked after this.

If I ever track down the root cause of this problem, I'll update the answer.