Re: Help! Error C2664 (cannot convert)

From:

"John Adams" <john@aol.com>

Newsgroups:

microsoft.public.platformsdk.com_ole,microsoft.public.vc.atl

Date:

Sat, 28 Jul 2007 14:11:17 -0700

Message-ID:

<#F#ravV0HHA.2312@TK2MSFTNGP05.phx.gbl>

note: PERSON_VECTOR should be BOOK_VECTOR in the code below.

"John Adams" <john@aol.com> wrote in message
news:eUpwNuV0HHA.3800@TK2MSFTNGP06.phx.gbl...

I'm trying to develop a very simple COM collection enumerator using ATL
(Visual Studio 2005 SP1). I want an object named ILibrary to return a
collection of IBook's. But I keep getting the same error in atlcom.h (line
211):

error C2664: '_CopyVariantFromInterface<T>::copy' : cannot convert
parameter 2 from 'IBook *const *__w64 ' to 'IBook **'

I don't know if I should be casting or converting anything myself. Below
is the relevant code.

Here's the library class:

typedef vector<IBook*> BOOK_VECTOR;
typedef CComEnumOnSTL<CComIEnum<VARIANT>, &IID_IEnumVARIANT, VARIANT,
_CopyVariantFromInterface<IBook>, PERSON_VECTOR > VarEnum;

class ATL_NO_VTABLE CLibrary:
public CComObjectRootEx<CComSingleThreadModel>,
public CComCoClass<CLibrary, &CLSID_Employer>, public
ICollectionOnSTLImpl<IDispatchImpl<ILibrary, &IID_ILibrary,
&LIBID_TestLib>,
BOOK_VECTOR, VARIANT, _CopyVariantFromInterface<IBook>, VarEnum>

Here's the copy policy class:

template < class T >
class _CopyVariantFromInterface
{
public:
static HRESULT copy(VARIANT* pV, T** pIP)
{
HRESULT hr = (*pIP)->QueryInterface(IID_IDispatch, (void**)&pV->pdispVal);
if(SUCCEEDED(hr) )
pV->vt = VT_DISPATCH;
else
{
(*pIP)->AddRef();
pV->vt = VT_UNKNOWN;
pV->punkVal = (*pIP);
}
return S_OK;
}

static void init(VARIANT* p) { VariantInit(p); }
static void destroy(VARIANT* p) { VariantClear(p); }
};

Please help!
Thanks.