in reply to Perl/Tk : Trouble with commands and Checkbuttons

Your code as posted doesn't compile. You've got a couple of typos in it...

Try this:

#! /usr/bin/perl 
use warnings;
use strict;
use Tk;

my $mw = MainWindow->new;
$mw->title("Checkbutton Grid");

my $x_size = 5;
my $y_size = 5;
my %b_name;

for (my $x=0; $x<$x_size; ++$x) {
  for (my $y=0; $y<$y_size; ++$y) {
    $mw -> Checkbutton (
           -activebackground => "white",
           -command => sub { print "$x,$y\n";
                       print "hi"; }
                       ) -> grid (
               -row => $x,
               -column => $y
                );
  }
}

MainLoop;

[download]

Note that when you want to call a subroutine in a -command line, you need to use the sub { ... } language. Note also that the values for $x and $y will be $x_size and $y_size respectively, because by the time you click on a check button, they've been incremented to those values - where they remain.

What you need to do is to associate a value (x, y) with each of the check buttons, and then use the value in your print statement.

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Re^2: Perl/Tk : Trouble with commands and Checkbuttons
by pg (Canon) on Sep 16, 2005 at 06:05 UTC

    This will not work, and will print 5,5 regardless which checkbutton you click. The issue is that you used the latest value of $x and $y, not the value at the time when the checkbutton is defined.

[reply]

      So a minor change to allow the closure to close on the current value would be to create new variables: 

      #! /usr/bin/perl 
use warnings;
use strict;
use Tk;

my $mw = MainWindow->new;
$mw->title("Checkbutton Grid");

my $x_size = 5;
my $y_size = 5;
my %b_name;

for (my $x=0; $x<$x_size; ++$x) {
    for (my $y=0; $y<$y_size; ++$y) {
        my $x_cord = $x;
        my $y_cord = $y;
        $mw -> Checkbutton (
                            -activebackground => "white",
                            -command => sub { print "$x_cord,$y_cord\n
+";
                                print "hi"; }
                           ) -> 
            grid (
                  -row => $x,
                  -column => $y
                 );
    }
}

MainLoop;

      [download]
      I'm not saying this is more efficient or better than your other example below (probably is neither), just that it's closer to the OP tried to do while still working.

[reply]
[d/l]

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