Hi Thomas,
Every COM object can only have a single IDispatch interface,
regardless how many other interfaces it may support. It is up to the
implementer of the object to make sure all the functionality of the different
VTBL interfaces is accessible to scripting languages through the IDispatch
interface.
Visual Basic is not using IDispatch, so it can access all COM
interfaces of an object. If you can find a way to access the functionality you
need from _vbscript_ (which is also restricted to IDispatch), then I’m sure there’ll
be a way to access it from Perl as well. But if there isn’t, then you may have
to implement a wrapper object in e.g. VB to expose the additional functionality
through IDispatch.
Cheers,
-Jan
From:
[EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED]
Sent: October 27, 2006 9:22 AM
To: perl-win32-users@listserv.activestate.com
Subject: OLE-object type cast
Hi,
in a project we
want to use the DCOM-API of a Win98-based measurement instrument.
We need to
access different so called Inputs which have some common settings but also some
individual settings.
This is mapped
to the API by creating a Class "IInput" (which is IDispatch type
according to OLEViewer.exe) for all the settings common to all the channels,
and to derive other Classes like "IBridgeInput" (which is IInput type
according to OLEViewer.exe) for the specific settings.
To my
understanding so far IBridgeInput inherits the structure from IInput and adds
the additional special features.
Well, so far so
good:
The problem arises
from the way of access to the objects.
+++The only
way+++ to access the API is by referencing a structure in a way like:
my $MyInput =
$InputBoard->Inputs->Item(3)
here the method
Item($i) return ++always++ an IInput-type, however the physical situation is:
Item(1) and
Item(2) are in fact IInput (only common settings)
Item (3) is an
IBridgeInput (certain special settings)
Item (4) is a
IIPCInput (other certain special settings)
Item(5) is a
ICounterInput (again other special settings)
The API defines
this types and exports them, i.e. when I do the same in Visual Basic I just do
Dim MyInput as
BridgeInput; REM make it a bridge input, no matter what is returned
Set MyInput =
InputBoard.Inputs.Item(3)
and violas, I
can access common ++and++ special settings.
So my question
is: Is there a way to cast an OLE-Object type onto an existing/returned
Object of parent-type.
Like:
my $MyInput =
$InputBoard->Inputs->Item(3);
castObjectType($MyInput,
BridgeInput); # function non-existent
which is a
replacement for the explicit "DIM .... as ...." in Visual Basic.
Sorry for the
long description, but it's a difficult issue I think,
TIA,
Thomas
--------------------------------------------------------------------------------------
Dr. Thomas Bruns
<[EMAIL PROTECTED]>
Physikalisch-Technische Bundesanstalt
Braunschweig
Arbeitsgruppen: 1.31 & 1.34
Bundesallee 100
Tel: 0531/592 - 1220
D-38116 Braunschweig Fax:
0531/592-69-1220
--------------------------------------------------------------------------------------
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