Re: copy from IUnknown* to CComObjectRoot

From:

PaulH <paul.heil@gmail.com>

Newsgroups:

microsoft.public.vc.atl

Date:

Fri, 27 Feb 2009 06:51:02 -0800 (PST)

Message-ID:

<0df0fef1-c959-4d87-bf66-1b3f0b70b032@o36g2000yqh.googlegroups.com>

On Feb 26, 6:43 pm, "Igor Tandetnik" <itandet...@mvps.org> wrote:

PaulH <paul.h...@gmail.com> 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 have a static XML schema that I'm trying to represent in a COM
object. So, if the XML looks like this:
    <TagA value="X" Name="Y">
        <TagB Name="Z" something="xyz">
            <TagC Value="Ugly" phone="on" brain="off">
            <TagC Value="Poor" phone="on" brain="mush">
            <TagC Value="Target" phone="on" brain="Jello">
            <TagC Value="Clue" phone="off" brain="on">
        <TagB>
    </TagA>

I'd have COM objects like:

    class CTagB : public CComObjectRootEx<>,
                           public CComCoClass<>,
                           public IDispatchImpl< CollectionType,...>
    {
        BEGIN_COM_MAP( CTagB )
            COM_INTERFACE_ENTRY( ITagB )
            COM_INTERFACE_ENTRY( IDispatch )
        END_COM_MAP()
        DECLARE_NO_REGISTRY()
        DECLARE_NOT_AGGREGATABLE( CTagB )
        DECLARE_GET_CONTROLLING_UNKNOWN()
        DECLARE_PROTECT_FINAL_CONSTRUCT()

        HRESULT FinalConstruct();
        void SetParent( ITagA* pParent );

        STDMETHOD( get_Parent )( ITagA** ppParent );
        STDMETHOD( get_Root )( ITagA** ppRoot );
        STDMETHOD( Add )( ITagC* pPackage );
        STDMETHOD( Remove )( long Index );
        STDMETHOD( Clear )( void );
        STDMETHOD( CreatePackage )( IPackage** ppPackage );

        friend MSXML2::IXMLDOMNodePtr operator <<
( MSXML2::IXMLDOMNodePtr node, const CTagB& osf );
        friend MSXML2::IXMLDOMNodePtr operator >>( const
MSXML2::IXMLDOMNodePtr node, CTagC& osf );

    protected:
        ITagA* pParent_;
    };

The CComObjectRoot<> static object hierarchy seemed to be a good way
to go. But, the problem is that I don't know how many <TagC/> elements
there will be. So CTagB has to be a collection. I could make it a
collection of ITagC*, but then I can't use the operator<<() to print
and set the XML behind the scenes as I could if it were a collection
of CTagC objects.

Also, every other object is created by doing something like:
    TagBPtr pTagBPtr = pTagAPtr->GetTagB();
But, TagC would have to be created by:
    TagCPtr pTagCPtr( CLSID_TagC );
which seems inconsistent.

What do you suggest?

Thanks,
PaulH