Callback from VB6 to C

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MT - 28 Dec 2004 01:49 GMT

aloha,
i have this activex exe that runs without problems
and provides a com interface to a C++ program
i have exposed one function and one event, also no problems
now they want to pass a pointer to a function so i can
callback the C++ program instead of raising the event
assuming this works to get the address of the C++ function

Public Sub SetCallBack(ByVal CallBackAddr As Long)
CallBackAddress = CallBackAddr
End Sub

how do i actually "call" the C++ function ?
thanks for any help
mike

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alpine - 28 Dec 2004 02:21 GMT

>aloha,
>i have this activex exe that runs without problems
[quoted text clipped - 11 lines]
>thanks for any help
>mike

That's the tough part. You can't call a function pointer in VB
without jumping through some pretty serious hoops. If you absolutely
must follow this direction, you should pick up a copy of Matt
Curland's Advanced VB6 book.

If the need for calling the pointer isn't set in stone, you may be
better off going another route. They could, for instance, provide a
method on a COM interface that is passed into your application that
you could then call. Or, they could export the function and you could
call it via a declare statement from your VB code.

HTH,
Bryan
____________________________________________________________
New Vision Software "When the going gets weird,"
Bryan Stafford "the weird turn pro."
alpine_don'tsendspam@mvps.org Hunter S. Thompson -
Microsoft MVP-Visual Basic Fear and Loathing in LasVegas

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VB Forum / COM / December 2004

Callback from VB6 to C