SAFEARRAYS with COM

[Michel Voide]

Hi -

I'm trying to use an in/out SAFEARRAY with COM and VC++ 5, but it doesn't
work very fine :

First, when I add the following definition to my dispatch interface IDL
[id(10), helpstring("method testSafeArrayInt")] HRESULT
testSafeArrayInt([in, out] SAFEARRAY(int) theArray, [in] int increment);

the wizard adds the following to the c++ file :

STDMETHODIMP SimpleTest1::testSafeArrayInt(SAFEARRAY ( int ) theArray,
int increment)
which of course is not understood by the c++ compiler .....

when I correct this to

STDMETHODIMP SimpleTest1::testSafeArrayInt(SAFEARRAY /*( int )*/ theArray,
int increment)

it says following :

C:\Program Files\DevStudio\VC\ATL\include\atlcom.h(162) : error C2259:
'CComObject<class SimpleTest1>' : cannot instantiate abstract class due to
following members:
C:\Program Files\DevStudio\VC\ATL\include\atlcom.h(162) : warning C4259:
'long __stdcall ISimpleTest1::testSafeArrayInt(struct tagSAFEARRAY *,int)' :
pure virtual function was not defined
C:\Program Files\DevStudio\VC\ATL\include\atlcom.h(162) : error C2259:
'CComObject<class SimpleTest1>' : cannot instantiate abstract class due to
following members:
C:\Program Files\DevStudio\VC\ATL\include\atlcom.h(162) : warning C4259:
'long __stdcall ISimpleTest1::testSafeArrayInt(struct tagSAFEARRAY *,int)' :
pure virtual function was not defined
C:\Program Files\DevStudio\VC\ATL\include\atlcom.h(874) : error C2259:
'CComContainedObject<class SimpleTest1>' : cannot instantiate abstract class
due to following members:
C:\Program Files\DevStudio\VC\ATL\include\atlcom.h(874) : warning C4259:
'long __stdcall ISimpleTest1::testSafeArrayInt(struct tagSAFEARRAY *,int)' :
pure virtual function was not defined

and if I make the final correction :

STDMETHODIMP SimpleTest1::testSafeArrayInt(SAFEARRAY* /*( int )*/ theArray,
int increment)
my server compiles, but returns a "type mismatch" error when I call the
function via COM, which is
normal, as this is not what I defined in the IDL !

Does anybody have a solution to this ?

Please help !

[Scott Rabon]

You might want to try using a VARIANT* type parameter, instead of the
SAFEARRAY parameter. And since you are using a dispatch interface, the
VARIANT type will be compatible with VB clients. So your function
declaration in the idl would look like:
HRESULT tesstSafeArrayInt( [in, out]VARIANT* theArray, [in]int increment);

Then access the SAFEARRAY in the VARIANT structure in your function.

Scott

Michel Voide wrote in message <36656...@epflnews.epfl.ch>...

[newgroups]

If you take this approach, you can find some text and a sample ATL project
with a VB6 client here:
http://www.arpsolutions.demon.co.uk/atl/atl_faq_001.htm

Scott Rabon wrote in message <8yf92.671$vR3....@news.ntplx.net>...

[Ben Hutchings]

Scott Rabon (sc...@eaglesol.com) wrote:
: You might want to try using a VARIANT* type parameter, instead of the

: SAFEARRAY parameter. And since you are using a dispatch interface, the
: VARIANT type will be compatible with VB clients. So your function
: declaration in the idl would look like:
: HRESULT tesstSafeArrayInt( [in, out]VARIANT* theArray, [in]int increment);

: Then access the SAFEARRAY in the VARIANT structure in your function.

<snip>

Don't forget to check that

variant.vt == (VT_ARRAY | VT_I4)
----- (or whatever the array should contain)

before accessing the array, though.

--
Any opinions expressed are my own and not necessarily those of Laser-Scan.

[Michel Voide]

Thank you all - it all works now....

But, just for curiosity ... I've read in some DCOM book that to send
directly a safearray, you
should use the following syntax in the IDL :
[in, out] SAFEARRAY(int) *myVar

Do you know if it is possible this way, or is it mandatory to use a VARIANT
type ? It seems at least that
the VC5 has a problem with this (refer to my previous message for more
infos....)

Thanks again ....

mvo