Re: ATL inheritance mistake

From:

"Igor Tandetnik" <itandetnik@mvps.org>

Newsgroups:

microsoft.public.vc.atl

Date:

Thu, 10 Dec 2009 07:49:07 -0500

Message-ID:

<eulBscZeKHA.6000@TK2MSFTNGP06.phx.gbl>

Barzo wrote:

But, using the COM_INTERFACE_ENTRY2(IDispatch, IAudioRecoder) I get
the following error:

error C2594: 'static_cast' : ambiguous conversions from
'CAudioRecorder::_ComMapClass *' to 'IAudioRecorder *'

Why it is ambiguous?

class ATL_NO_VTABLE CAudioRecorder :
  public IAudioRecorderImpl<CAudioRecorder>,
  public IDispatchImpl<IAudioRecorder, ...>

Your CAudioRecorder class derives from IAudioRecorder twice, once via =
IAudioRecorderImpl and again via IDispatchImpl. You want this instead:

class ATL_NO_VTABLE CAudioRecorder :
  public IDispatchImpl<IAudioRecorderImpl<CAudioRecorder>, ...>

Oh, and since you no longer derive from IDispatch twice, you don't need =
COM_INTERFACE_ENTRY2 - plain old COM_INTERFACE_ENTRY would do.
--
With best wishes,
    Igor Tandetnik

With sufficient thrust, pigs fly just fine. However, this is not =
necessarily a good idea. It is hard to be sure where they are going to =
land, and it could be dangerous sitting under them as they fly overhead. =
-- RFC 1925