COM Object

Bintuch has asked for the wisdom of the Perl Monks concerning the following question:

Kind monks,

I'm trying to interface some sort of Card Reader which I have COM object for. However, I can't get the value of the output parameters, but only the returned value of the function.

The 'Is_In' is output (not returned) parameter which suppose to detect the presence/absence of a card in the device.

I've checked COM object with VBScript and it's Ok. My code:

use Win32;
use Win32::OLE;
use Win32::OLE::Variant;

## Creating the 'Rdr' object - Ok

my $Status;
my $Is_In;
$Is_In = 0;
while (1) {
    $Status = $Rdr->IsCardIn($Is_In);
    print "Is Card In:$Status ; IsCardIn:$Is_In\n";
    sleep(1);
}
[download]

The $Is_In variable is never updated.

Can you please help?

Comment on COM Object Download Code

Replies are listed 'Best First'.
Re: COM Object by Jenda (Abbot) on May 11, 2010 at 14:55 UTC
I believe you have to predeclare the variable as VT_BYREF first. Something like: `my $Status; my $Is_In = Variant(VT_BYREF \| VT_VARIANT, 0); while (1) { $Status = $Rdr->IsCardIn($Is_In); print "Is Card In:$Status ; IsCardIn:$Is_In\n"; sleep(1); }` [download] Look at the "Variants by reference" section of the Win32::OLE::Variant docs. Jenda Enoch was right! Enjoy the last years of Rome.	[reply] [d/l]
Re^2: COM Object by Bintuch (Acolyte) on May 13, 2010 at 05:52 UTC
It Works!! Many Thanks	[reply]
Re: COM Object by bingos (Vicar) on May 11, 2010 at 10:28 UTC
Is this COM object documented somewhere? The only thing I can think of with the scant information provided is that perhaps you need to provide a scalar ref to the IsCardIn method `$Status = $Rdr->IsCardIn(\$Is_In);` [download]	[reply] [d/l]
Re^2: COM Object by Bintuch (Acolyte) on May 11, 2010 at 11:46 UTC
I've already tried this one.. No luck.. I have the usage for VBScript: `Dim is_in is_in=0 Do While is_in<>1 status=RDR.IsCardIn(is_in) CheckStatus status,"IsCardIn" Loop` [download] COM Object Function: `[id(0x0000000b), helpstring("method IsCardIn")] HRESULT IsCardIn( [out] VARIANT* is_in, [out, retval] VARIANT* status);` [download]	[reply] [d/l] [select]