Re: IXMLHTTPRequest AJAX trace

From:
"Igor Tandetnik" <itandetnik@mvps.org>
Newsgroups:
microsoft.public.vc.atl
Date:
Thu, 15 Jun 2006 13:29:44 -0400
Message-ID:
<Oto4wFKkGHA.3816@TK2MSFTNGP02.phx.gbl>
fongph@gmail.com wrote:

I implemented IClassFactory in my class and my class now inherits from
these classes
///////////////////////
class CCustomXMLHTTPRequest :
public IDispatchImpl<ICustomXMLHTTPRequest,
&IID_ICustomXMLHTTPRequest, &LIBID_IEEnumWindowsLib>,
public CComObjectRoot,
public CComCoClass<CCustomXMLHTTPRequest,&CLSID_CustomXMLHTTPRequest>,
public IXMLHTTPRequest,
public IClassFactory

////////////////////////
and the COM_MAP becomes
/////////////////////////
BEGIN_COM_MAP(CCustomXMLHTTPRequest)
COM_INTERFACE_ENTRY(ICustomXMLHTTPRequest)
COM_INTERFACE_ENTRY2(IDispatch, ICustomXMLHTTPRequest)
COM_INTERFACE_ENTRY2(IClassFactory,ICustomXMLHTTPRequest)
END_COM_MAP()


You still don't list IXMLHTTPRequest in your interface map.

COM_INTERFACE_ENTRY2(IClassFactory,ICustomXMLHTTPRequest)


Why COM_INTERFACE_ENTRY2? What relationship do you think IClassFactory
has with ICustomXMLHTTPRequest? For that matter, what is
ICustomXMLHTTPRequest and why do you think you need it at all?

////////////////////////
I also override the virtual functions of IClassFactory which are:
//////////////////////
//IClassFactory
STDMETHODIMP CCustomXMLHTTPRequest::CreateInstance(IUnknown
*pUnkOuter, REFIID riid, void **ppvObject)
{
if(pUnkOuter != NULL)
       return ResultFromScode(CLASS_E_NOAGGREGATION);

   return QueryInterface(riid, ppvObject);
}


Does CreateInstance get called at all? Probably not, due to your mangled
interface map.

I don't think you really want to return the same object for each
CreateInstance call. What if the script wants to run two or more
requests in parallel? What you want is to create two, I repeat _two_,
separate objects. One of them implements IXMLHTTPRequest. The other
implements IClassFactory. You create and register an instance of the
second one using CoRegisterClassObject. In its implementation of
CreateInstance, the second object creates an instance of the first
object - a _new_ one for every call.
--
With best wishes,
    Igor Tandetnik

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