in reply to Please review Class::WeakSingleton

Interesting - I don't know if I would still call this object a 'singleton' given this scope-based destruction, but I can understand the motivation and envision the requirements which has necessitated the development of this code.

One question however, why not inherit from Class::Singleton directly and simply weaken the reference returned - For example (untested code follows):

package Class::WeakSingleton;

use Class::Singleton;
use Scalar::Util ();

use vars qw/ @ISA /;
@ISA = qw/ Class::Singleton /;

sub instance
{
    my $class = shift;
    my $instance = $class->SUPER::instance( @_ );
    weaken( \$instance );
    return $instance;
}

1;

__END__

[download]

Update - Oops, my bad. Move along, nothing to see here ... :-)

 

perl -le 'print+unpack"N",pack"B32","00000000000000000000001001101100"'

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Re: Re: Please review Class::WeakSingleton
by diotalevi (Canon) on Jun 20, 2003 at 05:15 UTC

    instance() is not documented as being available for inheritance and I didn't immediately see a way of doing that with subclassing. Not that I can't be daft at times. I think though... that your fix doesn't do the job right. The stored reference needs to be weakened, not the returned reference.

[reply]
      Ahhh, excellent point ... One test which I think you should be performing however (and that with which I proved that my own code proposal did not work as intended) is the following which tests the out-of-scope destruction of your weakened reference - This is important because Class::Singleton would pass the test examples in your code, whereas only Class::WeakSingleton would pass this test.

      {
    my $g = wrapper->instance;
    $g->{'key'} = 'value';
}
$h = wrapper->instance;
die "Bad mojo!" if exists $h->{'key'};

      [download]

       

      perl -le 'print+unpack"N",pack"B32","00000000000000000000001001101101"'

[reply]
[d/l]

        Exactly. For the moment I just took the easy route and stole the existing test.pl. Its written up using some odd form of not-Test.pm and its ugly to behold. Yuck.

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