Re: Default Implementation for IUnknown

"Igor Tandetnik" <>
Thu, 3 May 2007 16:21:42 -0400
Stefan Weber <> wrote:

Why don't you just derive from IDispEvent[Simple]Impl?

Will try that, thank you.

They already
provide a suitable IUnknown implementation. No need for
CComObjectRootEx or IDispatch, and you get to use a sink map instead
of manually implementing a switch in Invoke. Parameter parsing and
coercion is also performed for you.

I need it for handling events registered in the browser's DOM. The
attachEvent method expects an IDispatch interface pointer and uses
Invoke as a callback.

Yes you can. Something like this:

class MySink : public IDispEventSimpleImpl<0, MySink, &IID_IDispatch> {
    typedef IDispEventSimpleImpl<0, MySink, &IID_IDispatch> BaseClass;
        SINK_ENTRY_INFO(0, IID_IDispatch, DISPID_VALUE, OnEvent,

    // |event| implements IHTMLEventObj[2|3|4]
    // return VARIANT_FALSE to cancel defaul action, VARIANT_TRUE to

    // Suitable for passing to attachEvent
    IDispatch* GetIDispatch() {

    static _ATL_FUNC_INFO EventInfo;

// In .cpp file
_ATL_FUNC_INFO MySink::EventInfo = {

With best wishes,
    Igor Tandetnik

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