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

I am working on an app for win NT4 with Tk with plans to export it with perl2exe. I have mulitiple windows that I would like to close with a exit button. I was thinking one sub with a var would be the shortest way of writting the code. (ex: 
sub close_win(var) {
     var->destory;
     }
button(-command=>\&close_win($thiswindow))->pack...

[download]
...) I can't seem to find how to write a function and pass a variable. Any suggestions on where to find the proper way of writting a function?

edited by ybiC: s/pre/code as per Monastery convention for example code

Replies are listed 'Best First'.
Re: Functions and Tk
by bobn (Chaplain) on Aug 24, 2003 at 01:30 UTC

    Here's an example that works: 

    #!/usr/bin/perl -w
use Tk;

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

my $HlpBttn = $mw->Button(-text=>"Make NEW Window", -command=> sub { m
+ake_win(); });
                       
$HlpBttn->pack(-padx =>60, -pady =>10);

MainLoop;

sub make_win 
{
    my $win = $mw->Toplevel(-title=>'new window');

    my $Bttn = $win->Button(-text=>"CLOSE this window",
                       -command=> sub { close_win($win); }
                   )->pack(-padx =>60, -pady =>10); 
}

sub close_win
{
    my $thiswin = $_[0];
    $thiswin->destroy;
}

    [download]

    make_win creates a closure in the -command option, creating an anonymous subref that carries around with it an instance of $win. When the "CLOSE this window" button is pressed in a given window, the coderef that is exectuted uses the instance of $win that it carries with it.

    Actually, I could have just said $win->Button(yada-yada...-command=> sub { $win->destroy })....

    Note that for either way to work, $win must be a lexical, outside the scope of the anonymous coderef.

    --Bob Niederman, http://bob-n.com

    All code given here is UNTESTED unless otherwise stated.

[reply]
[d/l]
[select]
      *yuck* That is a pretty obfuscated way of going about it -- Tk::callbacks 
      #!/usr/bin/perl -w
use Tk;

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

my $HlpBttn = $mw->Button(
    -text    =>"Make NEW Window",
    -command =>  [ \&makeWindow, $mw ], # calls makeWindow and passes 
+$mw as the first argument
);
                       
$HlpBttn->pack(-padx =>60, -pady =>10);


MainLoop;

sub makeWindow {
    my $parent = shift;
    my $win  = $parent->Toplevel(-title=>'new window');
    my $Bttn = $win->Button(
        -text=>"CLOSE this window",
        -command=>  [ 'destroy', $win ],  # calls destroy on $win
    )->pack(
        -padx =>60,
        -pady =>10,
    );
}
__END__

      [download]
      Sure closures aren't that obfuscated, but makeWindow needn't be tied to $mw (need not be a closure), and the "CLOSE this window" command need not be a closure either.

      MJD says "you can't just make shit up and expect the computer to know what you mean, retardo!"
      I run a Win32 PPM repository for perl 5.6.x and 5.8.x -- I take requests (README).
      ** The third rule of perl club is a statement of fact: pod is sexy.

[reply]
[d/l]
      I changed my code to match yours. There is still something wrong. I am getting the error. 
      Tk::Error AUTOLOAD 'Tk::Toplevel::destory' at line 97
Carp::croak at C:/usr/lib/Carp.pm line 191
Tk::Widget::__ANON__ at C:/usr/lib/Tk/Widget.pm line 338
main::Exit_Win at line 97
main::__ANON at line 82
[\&main::__ANON__ at line 82
Tk callback for .toplevel.frame2.button1
Tk::__ANON__ at C:/usr/lib/Tk.pm line 228
Tk::Button::butUp at C:/usr/lib/Tk/Button.pm line 111
[command bound to event]

      [download]
      $win->Button(...-command=> sub {$win->destory} )... Works great, but I would like to have the sub work.
[reply]
[d/l]

        It isn't really working. Tk::Error AUTOLOAD 'Tk::Toplevel::destory' at line 97 happend because you said ->destory when you meant ->destroy - and your window fgoes away because your program died.

        To make the subroutine work, I think the part you're missing is this: 

        doit('here is my input', 'some more');

sub doit
{
   my ( $in1, $in2 ) = @_;
   print "$in1\n";
   print "$in2\n";
}

        [download]

        subs all receive their parameters in @_ - then you transfer them in to local variables for readability, isolation, etc.

        In the orginal form of my example the line my $thiswin = $_[0]; in the close_win sub did this, just getting the first (and only) elment of @_;

        --Bob Niederman, http://bob-n.com

        All code given here is UNTESTED unless otherwise stated.

[reply]
[d/l]
[select]

        The answer is right in front of you: you misspelled destroy.

        converter

[reply]
      thanks for your help. passing vars to subs is something I haven't seemed to find yet. perldoc perlsub, if it says so, doesn't make it clear to a newbie.
      Thanks again, James
[reply]

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