Studio:Callback functions in Perl scripts

To use callback functions in Perl scripts, use LetProperty(). This is an ActiveState Perl requirement for assigning a COM object (e.g., another interface) to a read/write property.

The following example demonstrates a user callback registration service with an owner callback function:

# The following example illustrates how to script a function pointer

# that has been qualified with the scl_ptr_flist pragma. 

# Perspective: User of the regCallBack interface, Owner of the callBack interface

# Standard Perl setup

use strict;

use Carp;

use Win32::OLE;

Win32::OLE->Option(Warn => 3);


# Create a reference (shortcut) to the User instance of the regCallBack function

my $uRegCallBack = $main::ascript->Functions->Item("regCallBack")->User;


# Create a reference (shortcut) to the Owner instance of the regCallBack function

my $oCallBack = $main::ascript->Functions->Item("callBack")->Owner;


# Register for ownership of the callback function

$oCallBack->Register();


# Assign the callback function to the registration function's parameter cb

$uRegCallBack->ParameterList->LetProperty("cb", $oCallBack);


# Call the registration function passing in the callback function

$uRegCallBack->Call();


# Wait for the callback function to be called

my $event = $main::ascript->WaitForEvent();


# If the received event was the callback function

if ($event->Name == $oCallBack->Name) {

   # Process the function call

   # return the callback function to the user

   $oCallBack->Return();

}