Re: Calling subroutine with \& and passing variables

[Discipulus]

Hello IB2017,

this is covered in the Tk::callbacks basically you can pass any arguments you want as in: -dropcommand => [\&accept_drop, $drop, $another, $more] and they arrive in the sub accept_drop in @_ as always.

The same can be accomplished with:

[ \&subname, arg1,  arg2, ..]
# or 
[ sub { ... },arg1,  arg2, ..]

Note the [..] around sub and args: if more than one element is passed Tk will expect an anonymous array with the code reference as first element and arguments following.

Also note that the contents of the [..] are evaluated by perl when the callback is created.

PS see it in action:

perl -MTk -e "tkinit->Button(-text=>'print',-command=>[sub{print join'-',@_},1, 2,3])->pack;MainLoop"

L*

[IB2017]

Thank you for your suggestions. But I had already tried both your solutions and they did not work. See the following - code which I slighly modified to use your proposed solution \&subname, arg1, arg2, .. . PS: the code should print in the subrutine the variable $SomeVariable.

#!/usr/local/bin/perl -w

use Tk;
use Tk::DropSite;
use strict;
use vars qw($top $drop);

$top = new MainWindow;
$top->Label(-text => "The drop area:")->pack;
$drop = $top->Scrolled('Listbox',
               -scrollbars => "osoe",
              )->pack;
              
my $SomeVariable="xxx"; # The variable I want to pass to the subrutine

$drop->DropSite
  (-dropcommand => [\&accept_drop, $drop, $SomeVariable],
   -droptypes => ($^O eq 'MSWin32' ? 'Win32' : ['KDE', 'XDND', 'Sun'])
  );
MainLoop;

sub accept_drop {
    my($widget, $selection, $SomeVariable) = @_;
    
    print $SomeVariable;#printing the variable passed from the main
    
    my $filename;
    eval {
    if ($^O eq 'MSWin32') {
        $filename = $widget->SelectionGet(-selection => $selection,
                          'STRING');
    } else {
        $filename = $widget->SelectionGet(-selection => $selection,
                          'FILE_NAME');
    }
    };
    if (defined $filename) {
    $widget->insert(0, $filename);
    }
}

__END__

[IB2017]

Of course it works! It was the order of the passed variables that was wrong! For the sake of it, here it is the working code.

#!/usr/local/bin/perl -w

use Tk;
use Tk::DropSite;
use strict;
use vars qw($top $drop);

$top = new MainWindow;
$top->Label(-text => "The drop area:")->pack;
$drop = $top->Scrolled('Listbox',
               -scrollbars => "osoe",
              )->pack;
              
my $SomeVariable="xxx";

$drop->DropSite
  (-dropcommand => [\&accept_drop, $drop, $SomeVariable],
   -droptypes => ($^O eq 'MSWin32' ? 'Win32' : ['KDE', 'XDND', 'Sun'])
  );
MainLoop;

sub accept_drop {
    my ($drop, $SomeVariable, $selection) = @_;
    
    print "This is my variable passed from the main: $SomeVariable\n";
    
    my $filename;
    eval {
    if ($^O eq 'MSWin32') {
        $filename = $drop->SelectionGet(-selection => $selection,
                          'STRING');
    } else {
        $filename = $drop->SelectionGet(-selection => $selection,
                          'FILE_NAME');
    }
    };
    if (defined $filename) {
    $drop->insert(0, $filename);
    }
}

__END__