Is there a better way to create an object?

From:

Barzo <dbarzo@gmail.com>

Newsgroups:

microsoft.public.vc.atl

Date:

Mon, 12 Oct 2009 07:15:06 -0700 (PDT)

Message-ID:

<09efe6dc-96a1-4a0d-9d00-1c0160c65e43@v25g2000yqk.googlegroups.com>

Hi,

in my project I have a "noncreatable" object.
The IDL (simplified) is the following:

[
  object,
  uuid(AB566C6D-AF54-11DE-B5BE-00A0D15E9B20),
  oleautomation,
  nonextensible,
  helpstring("InterfaceA Interface"),
  pointer_default(unique)
]
interface IAudioMixer : IUnknown
{
  [propput, id(1)]
  HRESULT PropertyA([in] short arg);
  [propget, id(1)]
  HRESULT PropertyA([out, retval] short* pVal);
};
//--------------------------------------------------
[
  uuid(AB566C6F-AF54-11DE-B5BE-00A0D15E9B20),
  dual,
  nonextensible
]
interface IAudioPlayer : IDispatch
{
  [propget, id(3), helpstring("Returns a reference to a IAudioMixer
interface.")]
  HRESULT GetMixer([out, retval] IAudioMixer** pVal);
};

//--------------------------------------------------

[
  uuid(AB566C66-AF54-11DE-B5BE-00A0D15E9B20),
  version(1.0),
  helpstring("....")
]
library MyLibrary
{
  importlib("stdole2.tlb");

  [
    uuid(AB566C72-AF54-11DE-B5BE-00A0D15E9B20),
    helpstring("AudioPlayer Class")
  ]
  coclass AudioPlayer
  {
    [default] interface IAudioPlayer;
  };

  [
    uuid(AB566C80-AF54-11DE-B5BE-00A0D15E9B20),
    noncreatable,
    helpstring("AudioMixer Class")
  ]
  coclass AudioMixer
  {
    [default] interface IAudioMixer;
  };
}

Now, in the CAudioPlayer class I have a member:

CComPtr<IAudioMixer> mixer_;

and in the FinalConstruct I have to create the object:

CAudioMixer* p_mixer;
IAudioMixer* i_mixer;

HRESULT hr = CComCoClass<CAudioMixer>::CreateInstance(&i_mixer);

if (SUCCEEDED(hr))
{
  p_mixer = dynamic_cast<CAudioMixer*>(i_mixer);
  p_mixer->SetMixerObj( player_->getAudioMixer() );
  mixer_.Attach(i_mixer);
}

I coded in this way because CAudioMixer::SetMixerObject is not part of
the IAudioMixer interface.
Is there a better way to do the same job?

Thanks,
Daniele.