WeakRef(3) User Contributed Perl Documentation WeakRef(3)NAMEWeakRef-- an API to the Perl weak references
SYNOPSIS
use WeakRef;
for($i=0; $i<100000; $i++) {
my $x = {};
my $y = {};
$x->{Y} = $y;
$y->{X} = $y;
weaken($x->{Y});
} # no memory leak
if(isweak($ref)) {
}
DESCRIPTION
A patch to Perl 5.005_55 by the author implements a core API for weak
references. This module is a Perl-level interface to that API, allowing
weak references to be created in Perl.
A weak reference is just like an ordinary Perl reference except that it
isn't included in the reference count of the thing referred to. This
means that once all references to a particular piece of data are weak,
the piece of data is freed and all the weak references are set to
undef. This is particularly useful for implementing circular data
structures without memory leaks or caches of objects.
The command
use WeakRef;
exports two symbols to the user's namespace by default: "weaken" and
"isweak". "weaken" takes a single argument, the reference to be
weakened, and returns the same value. The idiom
weaken($this->{Thing}->{Parent} = $this);
is useful.
The "isweak" command takes a single parameter and returns true if the
parameter is a weak reference, undef otherwise.
BUGS
None known.
AUTHOR
Tuomas J. Lukka lukka@iki.fi
Copyright (c) 1999 Tuomas J. Lukka. All rights reserved. This program
is free software; you can redistribute it and/or modify it under the
same terms as perl itself.
BLATANT PLUG
This module and the patch to the core Perl were written in connection
with the APress book `Tuomas J. Lukka's Definitive Guide to Object-
Oriented Programming in Perl', to avoid explaining why certain things
would have to be done in cumbersome ways.
perl v5.18.1 1999-02-23 WeakRef(3)
