Re: Default Implementation for IUnknown

From:
"Alexander Nickolov" <agnickolov@mvps.org>
Newsgroups:
microsoft.public.vc.atl
Date:
Fri, 4 May 2007 10:05:13 -0700
Message-ID:
<#ypni5mjHHA.4768@TK2MSFTNGP05.phx.gbl>
No, your class does not implement IUnknown. CComObject<>
works by deriving from your class and providing implementation
for the 3 IUnknown methods thus populating the vtables of all
COM interfaces implemented by your class. The rest of your
speculations are meaningless in this new light.

--
=====================================
Alexander Nickolov
Microsoft MVP [VC], MCSD
email: agnickolov@mvps.org
MVP VC FAQ: http://vcfaq.mvps.org
=====================================

"Stefan Weber" <stefan.weber@gmail.com> wrote in message
news:1178222614.590137.126810@p77g2000hsh.googlegroups.com...

I second Igor's suggestion about IDispEvent[Simple]Impl.


As already mentioned in the answer to Igor's suggestion: Does this
also work in the situation when the event handler is registered with
the IHTMLElement2::attachEvent event method?

Just to answer your question, you need to wrap your object
in CComObject<> or one of its siblings to get an IUnkown
implementation:

CComObject<DOMEventHandler>* pObj = NULL;
HRESULT hr = CComObject<DOMEventHandler>::CreateInstance(&pObj);
pObj->GetUnknown()->AddRef();
// Use it here
pObj->GetUnknown()->Release();


Hmm, I kind of have a hard time to understand this... the idea of this
class seems to wrap a object, such that it can be accessed like any
other COM object?

Now, I assume IUnknown is already implemented by DOMEventHandler. In
this case, do I need to create the instance with CreateInstance
method? I mean, as long as I do the reference counting properly, it
doesn't really matter if I access it via a COM interface pointer or
via the C++ vtbl, right? Or would this be bad practice?

By the way, I think this class has to be declared as aggregatable:
first, it is created within an other COM object and second, it is
registered as an event handler (i.e. aggregated somewhere in the DOM).
Is this correct?

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