Hello monks,

I have a fairly large object framework, many parts of which use a singleton-type class, which contains quite a lot of state, and manages many other types of object.

When I wrote it, I intended that the first call to the constructor would return the "master" reference, subsequent calls would return weak references.

Unfortunately, I didn't test that this did what I expected, indeed perldoc Scalar::Util says

Note that if you take a copy of a scalar with a weakened reference, th
+e copy will be a strong reference.

    my $var;
    my $foo = \$var;
    weaken($foo);                       # Make $foo a weak reference
    my $bar = $foo;                     # $bar is now a strong referen
+ce

[download]
My problem (and a possible solution) is demonstrated in this snippet:
/usr/bin/perl
use strict;
use Scalar::Util qw/weaken isweak/;
my $foo = {};

my $bar = returnweak();
print "returnweak isweak - ".(isweak($bar)? "yes":"no")." - '$bar'\n";

weakenbyref(\$bar);
print "weakenbyref isweak - ".(isweak($bar)? "yes":"no")." - '$bar'\n"
+;

sub returnweak {
        my $ret = $foo;
        weaken($ret);
        return $ret;
}

sub weakenbyref {
        my $arg = shift;
        weaken($$arg = $foo);
        return;
}

[download]

which outputs:

returnweak isweak - no - 'HASH(0x606df0)'
weakenbyref isweak - yes - 'HASH(0x606df0)'

[download]

However passing a reference to the scalar which will contain the objectref is an unusual constructor, and would require changes to all callers, which I'd like to avoid if possible.

Is there a solution which does what I want (create a really weak reference which when copied/assigned, remains weak), and doesn't require a change in all calling code? Something like Scalar::Util::cripple :-)

Thanks



Pete

In reply to return weak reference by flipper

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