#!/usr/bin/perl
use strict;
use warnings;
use Tk;
use Tk::DialogBox;
use Tk::JComboBox;

# example by grandfather of perlmonks.org
# shows how to make the textvariable ref update
# see other example
my $main = MainWindow->new (-title => "Test JComboBox");
EditPlayers ($main);

sub EditPlayers {
    my ($main, $sel) = @_;
    my @ids = qw(Fred Joe Bob);
    my $dlg = $main->DialogBox (-title => "Member Information", -butto
+ns => ["OK", "Cancel"]);
    my $id = $sel || (@ids && $ids[0]) || '';
    my $IDText = $dlg->add (
        'JComboBox',
        -mode => 'readonly',
        -selectcommand => [\&changeEditPlayer, \$id],
        -validate => 'match',
        -textvariable => \$id,
        );
    
    $IDText->form (-left => '%0', -right => '%100', -top => '%0');
    $IDText->configure (-options => \@ids);

    #$IDText->setSelected ($id); # dosn't work
    $IDText->setSelected ($sel || (@ids && $ids[0]) || ''); #works

    return if $dlg->Show (-global) ne 'OK';
}


sub changeEditPlayer {
    my ($id, $widget, $index, $value, $name) = @_;

    return 1 if ! defined $name;
    print "$name\n";
}
[download]

An interesting note:

If we insert some 'print' statements, we can see that the $dlg->add() function resets the value of $id, I am assuming because it does not match any of the 'valid' options.

#... code 

    my $id = $sel || (@ids && $ids[0]) || '';
    
    print "id 1 is <$id>\n";

    my $IDText = $dlg->add (
        'JComboBox',
        -mode => 'readonly',
        -selectcommand => [\&changeEditPlayer, \$id],
        -validate => 'match',
        -textvariable => \$id,
        );
    
    print "id 2 is <$id>\n";
[download]

What is also interesting, is that we cannot set $id to anything now that is associated with the readonly JComboBox. However, once the options are defined, $id can be set, but only to a valid option.

    $id = "Joe";print "id is not Joe!! <$id>\n";

    $IDText->form (-left => '%0', -right => '%100', -top => '%0');
    $IDText->configure (-options => \@ids);

    # not only sets the selection but calls <c>changeEditPlayer</c>

    $id = "Joe"; print "now id is not empty!! <$id>\n";

    # does nothing, because 'Sandy' is not a valid option

    $id = "Sandy"; print "id not set to Sandy because it is an invalid
+ option <$id>\n";

    $id = $sel || (@ids && $ids[0]) || '';
    
    ### now it works !!

    $IDText->setSelected ($id); # dosn't work
[download]

With the print statement modified slightly in changeEditPlayer, we get the following results (without any clicking of the mouse!)

id 1 is <Fred>
id 2 is <>
id is not Joe!! <>

 - inside changeEditPlayer Joe

now id is not empty!! <Joe>
id not set to Sandy because it is an invalid option <Joe>

 - inside changeEditPlayer Fred
[download]

Honestly, I was a bit confused when I was first playing with this bit of code. Never had I seen a straight declaration, like the following, not work.

$id = 'Sandy';
print "<$id>\n";  # prints Joe
[download]

FWIW, if you really look into how the -validate callback works for most widgets that have it, the results are confusing.....in other words....it's tricky to get validate to do what you want. Check out Simple Tk Gauge for an interesting trick.

---

I'm not really a human, but I play one on earth.
Old Perl Programmer Haiku

Please post additional code (wrapped in <code> tags - Writeup Formatting Tips). If possible, make as short as you can, but a monk who wants to help should be able to just download it, run it and see the behavior you are having trouble with.