I needed Class::Singleton to expire its objects on some sort of schedule instead of the default immortality. In my case I want to create a sort of session object for a database wrapper, be able to find this data globally (hence the Singleton pattern) but still have it expire when then the session object goes out of scope of the containing routine. Hence Class::WeakSingleton. I'm going to upload it to CPAN but I want to get some feedback from anyone who feels like it on either implementation, style or whatever works.

{
    my $c = wrapper->instance;
    my $d = wrapper->instance;
    die "Mismatch" if $c != $d;
}   # wrapper->instance expires
{
    my $e = wrapper->instance;
    {
        my $f = wrapper->instance;
        die "Mismatch" if $e != $f;
    }
}   # wrapper->instance expires

package wrapper;
BEGIN { our @ISA = ('Class::WeakSingleton') }
sub ::DEBUG { 1 }
my $count = 0;
sub _new_instance {
    print "_new_instance()\n" if ::DEBUG;
    bless { (++$count) x 2 }, shift;
}

package Class::WeakSingleton;
use Scalar::Util ();

sub instance {
    my $class = shift;

    # get a reference to the _instance variable in the $class package
    no strict 'refs';
    my $instance = "${class}::_instance";

    return $$instance if defined $$instance;

    my $new_instance = $class->_new_instance(@_);
    $$instance = $new_instance;

    Scalar::Util::weaken( $$instance );

    return $new_instance;
}

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In reply to Please review Class::WeakSingleton by diotalevi

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