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

Hi, I have this error when I select different month in the drop down box then hit "print value" any body know why or how to fix the error? There are no error if I don't click on the drop down.

Thanks in advance.

Tk::Error: Can't call method "butUp" on an undefined value at C:/Perl/site/lib/T k/BrowseEntry.pm line 375. <ButtonRelease-1> (command bound to event) Code 

# BrowseEntry, entry with listbox to select list values.

use strict;
use warnings;
use Tk;
use Tk::BrowseEntry;

my $month = "January";


    my $top = MainWindow->new;
    my $f = $top->Frame->pack;
    my $top_f = $f->Frame(-bg=>'red', -width=>'200')->pack;
    my $bot_f = $f->Frame(-bg=>'red', -width=>'200')->pack;
    my $c = $top_f->BrowseEntry(-label => "Month:", -variable => \$mon
+th);
    $c->pack;
    $c->insert("end", "January");
    $c->insert("end", "February");
    $c->insert("end", "March");
    $c->insert("end", "April");
    $c->insert("end", "May");
    $c->insert("end", "June");
    $c->insert("end", "July");
    $c->insert("end", "August");
    $c->insert("end", "September");
    $c->insert("end", "October");
    $c->insert("end", "November");
    $c->insert("end", "December");

    
    $bot_f->Button(-text => "Print value",
        -command => sub {
            print "The month is $month\n";
            $top_f->destroy if Tk::Exists($top_f);
        }, -relief => "raised")->pack;

    
    
    MainLoop;

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Replies are listed 'Best First'.
Re: Perl TK BrowseEntry error
by stefbv (Priest) on Jan 10, 2010 at 17:20 UTC

    Do you really need to destroy the 'top_f' frame? If you comment the line

    $top_f->destroy if Tk::Exists($top_f);

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    then the error will vanish.

    I presume is a normal error for the way you use destroy, but I don't know enough about the internals of Tk to give you a technical explanation.

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Re: Perl TK BrowseEntry error
by biohisham (Priest) on Jan 10, 2010 at 17:58 UTC
    I can't explain the error that you're getting effectively, it seems that there's a widget event associated with the mouse left button release click. Here is another way to do it...by using a "scrolled Listbox" and by double clicking on a month you can get its corresponding value printed to the console, also you can do the same from clicking the button as you've originally intended: 
    #!/usr/local/bin/perl
use strict;
use warnings;
use Tk;

my $mainWindow = MainWindow->new(-title=>"Main Window");
my $listBox = $mainWindow->Scrolled(
   'Listbox',
   -scrollbars=>'e'
   )->pack;
$listBox->insert('end',qw(Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov
+ Dec));

$listBox->bind('<Double-1>', \&getActive);
$mainWindow->Button(
                    -text=>'print value',
                    -command=>\&getActive,
                    )->pack();

sub getActive{
    my $month;
    $month = $listBox->get('active');  #detects a selected list item
    print  $month,"\n";
    };
    

MainLoop;

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    Update: On closer inspection, why do you want to destroy the frame "$top_f" since it contains the widget that lets you browse the months collection? 

    my $button=$top->Button(
   -text=>'Print Value',
   -command => \&printMonth,
   #-relief=>'raised'
   )->pack();
   
sub printMonth{
    print "The Current Month is $month\n";
    }

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    Excellence is an Endeavor of Persistence. Chance Favors a Prepared Mind.
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Re: Perl TK BrowseEntry error
by ldln (Pilgrim) on Jan 10, 2010 at 18:54 UTC
    Think this behavior is caused by small bug in BrowseEntry.

    Try replacing: 

    $top_f->destroy if Tk::Exists($top_f);
with
$top_f->packForget( ) if $top_f->ismapped;

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Re: Perl TK BrowseEntry error
by fast (Novice) on Jan 10, 2010 at 19:46 UTC
    Thank you all for reply. This is just an example code. The reason I destroy the top_f is because I want to replace with a different screen after the user finish selecting. I think "ldln" is right about the bug in BrowseEntry widge.
    Is packForget similar to destroy?.
    $top_f->packForget( ) if $top_f->ismapped;
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      Hi,

      packForget will hide the widget. You can call pack on it to display it again. The instance will stay in memory. Unless you need $top_f again, you could use afterIdle to delay destroying the frame until the Buttons -command-callback has returned: 

          $bot_f->Button(-text => "Print value",
        -command => sub {
            print "The month is $month\n";
            $top->afterIdle(sub{
            $top_f->destroy if Tk::Exists($top_f);
            });
        }, -relief => "raised")->pack;

      [download]

      Cheers, Christoph
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