in reply to what is difference between calling the function in Perl/Tk in the following ways

A colleague of mine recomends the first approach. The second one sometimes leads to memory leaks, if the button itself is passed as one of the parameters to the sub.
  • Comment on Re: what is difference between calling the function in Perl/Tk in the following ways

Replies are listed 'Best First'.
Re^2: what is difference between calling the function in Perl/Tk in the following ways
by runrig (Abbot) on Apr 16, 2010 at 00:08 UTC
    I'd expect a memory link from code like:
    my $button;
$button = $frame->Button(... , -command => sub { SomeFunction($button)
+ });

    [download]
    But it should only matter if the button is created more than once (and I'd only worry about that if it's created many times). On a single-window app where you only create widgets once, it really doesn't matter. If it does matter, then you can probably use Scalar::Util::weaken() to get around it (but by then I'd agree that it's probably easier to use the first method).
[reply]
[d/l]
Re^2: what is difference between calling the function in Perl/Tk in the following ways
by ikegami (Patriarch) on Apr 16, 2010 at 14:53 UTC
    I don't see how one could leak and not the other. You could always change 
    (-command=>sub {&function($arg1,$arg2)});

    [download]
    to 
    (-command=>[sub {&function($arg1,$arg2)}]);

    [download]
    but I suspect that's already happening internally.
[reply]
[d/l]
[select]
      It's the circular reference preventing garbage collection that would cause the leak. The same sort of leak that happens when you repeatedly create anonymous recursive subs like:
      my $fact;
$fact = sub {
  my $n = shift;
  return $n if $n <= 1;
  return $n*fact($n-1);
}

      [download]
      Hmm, you're right, the other one would probably leak also if they both contain $button. (update: oops...looking at wrong thread since the OP didn't even have a circular reference in the example).
[reply]
[d/l]
[select]

        the other one would probably leak also if they both contain $button

        Exactly. 

        my $obj;
my $obj = { data => [ \&f, \$obj ] };       # leaks

my $obj;
my $obj = { data => [ sub { f($obj) } ] };  # leaks

my $arg;
my $obj = { data => [ \&f, \$arg ] };       # doesn't leak

my $obj;
my $obj = { data => [ sub { f($arg) } ] };  # doesn't leak

        [download]
[reply]
[d/l]
      Both these two would leak, I fear. The only safe way is to call 
      -command=>[\&function,\$arg1,\$arg2]

      [download]
[reply]
[d/l]

        By adding \$arg1,\$arg2, the memory leak goes away? I don't think so.

[reply]
[d/l]

In Section Seekers of Perl Wisdom