Re: copy from IUnknown* to CComObjectRoot

PaulH <>
Fri, 27 Feb 2009 07:56:01 -0800 (PST)
On Feb 26, 6:43 pm, "Igor Tandetnik" <> wrote:

PaulH <> wrote:

I have an ATL COM object that implements an ATL collection of another
ATL COM object. What I would like to do is essentially what I have in
the code below, I'm just not sure how to implement it. As is, the code
compiles, but when I read the iterator back, the collection is full of
empty objects suggesting the copy isn't deep enough.

typedef std::vector< CComObjectEmbed< CMyObj > > ContainerType;

STDMETHODIMP CMyCollection::Add( IMyObj* pObj )
   CComObjectEmbed< CMyObj > item;
   item = pObj; // ???

This compiles because CComObjectEmbed has this constructor:

CComObjectEmbed(void* pv) {m_pOuterUnknown = (IUnknown*)pv;}

As you see, what it does is nowhere near what you seem to think it does.

I'm not sure what you are trying to achieve. Why not just have a
collection of IMyObj* pointers? Note that there's no guarantee that
there's an instance of CMyObj behing IMyObj*. Somebody could provide
their own implementation of IMyObj, and pass that to you.
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

I think I've got it figured out. Copying isn't the answer. "Jason S"
had the same problem a couple of years ago:

Feel free to tell me if this is a bad idea, but I went with:
    typedef std::vector< CComObjectEmbed< CPackage > > ContainerType;
    STDMETHODIMP CTagB::CreateTagC( ITagC** ppTagC )
        CComObjectEmbed< CTagC > tagc;
        tagc.SetParent( this );
        tagc.SetOuterUnknown( GetControllingUnknown() );
        HRESULT hrTagC = tagc.FinalConstruct();
        if( FAILED( hrTagC ) )
            return hrTagC ;

        m_coll.push_back( tagc);
        return m_coll.rbegin()->QueryInterface( ppTagC );

So, when you create a TagC, it's automatically added to TagB.


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