Re: I have a VB project, but VC/COM question(s)

From:
"Igor Tandetnik" <itandetnik@mvps.org>
Newsgroups:
microsoft.public.vc.language
Date:
Sat, 29 Mar 2008 10:55:22 -0400
Message-ID:
<OMRjtzakIHA.980@TK2MSFTNGP06.phx.gbl>
"Ralph" <nt_consulting64@yahoo.com> wrote in message
news:OJCs%23dXkIHA.5084@TK2MSFTNGP04.phx.gbl

A SCODE is an HRESULT. You are correct though that VB is not going to
catch the return - because there ain't no "return". The method
doesn't define one.


What do you mean, doesn't define one? The IDL definition clearly states:

   dispinterface IPartDoc {
        properties:
        methods:
            [id(0x00000001)]
            SCODE SetPartData(...);

This is a pure dispinterface, not a custom or dual interface. An
equivalent definition in, say, a dual interface would go like this:

[dual]
IPartDoc : IDispatch {
    [id(0x00000001)]
    HRESULT SetPartData(..., [out, retval] SCODE* ret);

The SCODE value is being returned via pVarResult parameter of
IDispatch::Invoke - in addtition to the HRESULT value that Invoke itself
returns.

Basically, whoever designed this interface made the same mistake you are
making, in not understanding how dispinterfaces differ from regular
interfaces. You don't normally have a dispinterface method return
HRESULT (or SCODE) because it's redundant.
--
With best wishes,
    Igor Tandetnik

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