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Checkbutton in a loop

by gocpon (Novice)
on Apr 29, 2012 at 05:03 UTC ( #967899=perlquestion: print w/ replies, xml ) Need Help??
gocpon has asked for the wisdom of the Perl Monks concerning the following question:


I create a checkbutton in loop, If I check any of the checkbutton i am not getting -text of the corresponding checkbutton .Kindly help me

#! c:\perl\Bin use Tk; use Tk::Pane; use Tk::CheckButton; use Tk::LabFrame; @a=qw/one two three four five six seven eight nine ten/; $mw = MainWindow->new; $mw->geometry('200x200'); $f = $mw->Scrolled("Frame",-borderwidth => 3, -relief => 'groove',-hei +ght=>20)->pack; #$scrollbar = $f->Scrollbar(-orient => 'vertical'); $j=0; foreach $i(1...20) { $c=$f->Checkbutton(-text=>$a[$j],-command=>\&fun)->pack(); $i++; $j++; } MainLoop; sub fun { print ("$a[$j]"); }

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Re: Checkbutton in a loop
by Eliya (Vicar) on Apr 29, 2012 at 08:37 UTC

    What do you expect $j to be when the callback function gets called?  You have to somehow pass it as an argument to the routine.  There are two ways to pass the value:

    Either specify an array(ref) to the -command option

    ... for my $i (0...$#a) { $f->Checkbutton(-text => $a[$i], -command => [ \&fun, $i ] )->pack +(); } MainLoop; sub fun { my $j = shift; print $a[$j]; }

    Or use a closure

    ... for my $i (0...$#a) { $f->Checkbutton(-text => $a[$i], -command => sub { fun($i) } )->pa +ck(); } ...

      There is a third option, don't pass it any arguments

      use Tk; $mw = tkinit; for(1..4){ $mw->Checkbutton( -text => qq/check it $_/, -command => \&f, ) ->pack; } MainLoop; sub f { my $b = $Tk::event->W; warn join q/ /, $b->{Value}, $b->cget(q/-text/); } __END__ 1 check it 3 at - line 14. 0 check it 3 at - line 14. 1 check it 3 at - line 14. 0 check it 3 at - line 14. 1 check it 3 at - line 14. 0 check it 3 at - line 14. 1 check it 3 at - line 14. 0 check it 3 at - line 14.
Re: Checkbutton in a loop
by zentara (Archbishop) on Apr 29, 2012 at 13:30 UTC
    Others have given good answers to your question, but neglected to chastise you for your lousy code. So just in case this is homework, I offer these comments.:-)

    First off, if you added

    use warnings; use strict;
    you would have received a fatal error that there is no Tk::CheckButton module. Fix that error, then you load Tk::LabFrame but never use it. Instead you use Tk::Pane to make a scrolled frame, which has its packing options unset, so the whole checkbutton list is crushed to 1 entry. You even use the .. operator incorrectly, but luckily it seems to work.
    foreach $i (1...20) # that ... should be ..
    Your @a array only has 10 elements one to ten, but you make 20 checkbuttons.

    If you are a student, I wouldn't even accept this as a valid submission. Here is some unflawed code for you to look at.

    #!/usr/bin/perl use warnings; use strict; use Tk; use Tk::Pane; my @a=qw/one two three four five six seven eight nine ten/; my $mw = MainWindow->new; $mw->geometry('200x200'); my $f = $mw->Scrolled("Frame",-borderwidth => 3, -relief => 'groove',- +height=>20) ->pack(-expand=> 1, -fill=>'both'); foreach my $i (0 .. 19){ # this should be foreach my $i (@a), but it' +s your code :-) print "$i\n"; my $c = $f->Checkbutton(-text=>$a[$i],-command=>[ \&fun, $a[$i] ] )->p +ack(); $i++; } MainLoop; sub fun{ print "@_\n"; }

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

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