Gary Stainburn wrote:
> Hi folks,
>
> My first forrey into Perl objects sees me trying to model a railway. I've got
> a hash of named blocks of track, which is added to when I create a new block
> object.
>
> My problem is one of destroying a block (object), making sure that I have no
> memory leakage.
>
> I create a new track block such:
>
> my $T1=Trainset->track('T1','Block');
>
> This also created $Trainset::_BLOCKS{T1} which references the object.
Hi Gary,
I really think your problem comes in here. I would always be leery of situations
where you have to use the namespace prefix explicitly. It generally casts too
broad a net for most purposes. I think you are doing the right thing--sort
of--with Trainset. This is assumig that you have a Trainset class as well as a
Track class. I would suggest, though, that you assign new $track to your object
through $train_set, your Trainset object, rather than through the class itself.
This apporoach would give you the flexibility to have mutliple Trainset objects,
thus make your class more robust.
>
>
> My problem is how can I destroy the object when I no longer want it?
>
> If I call
>
> $T1=$T1->delete;
>
> Then the object is destroyed (display in DESTROY shows this). However, if I
> simply call
>
> $T1->delete;
>
> The object isn't destroyed because even though the ref in %_BLOCKS is deleted,
> the ref in $T1 is still there. Is there and way to ensure that the object is
> destroyed - i.e. force the refcount to zero?
>
> The only solution I've come up with is to explicitly call DESTROY from within
> the delete function, and within DESTROY empty the hash. Is this sufficient,
> or will this still tie up memory? Is there a better way?
>
> --
> Gary Stainburn
Overall, I would suggest that you steer clear of internal references in your
objects when possible. It is much better to make a container class, then delete
contained objects from the container. Generally you would want to avoid having
other references to the contained objects, except through the methods of the
container [Trainset] object.
package Trainset;
use strict, warnings et. al.;
use Exporter;
our @ISA = qw/Eporter/;
sub new {
my $class = shift;
my $self = {};
bless $self, $class;
$self->initialize(@_);
}
sub initialize {
my $self = shift;
$self->{'set ID'} = shift;
#... assign other set-level scalar info hard-coded into
# the parameter list ...then:
push @{$self->{'tracks'}}, (@_}; # to allow initialization with an existing
list
}
sub add_track {
my $self = shift;
my $track = shift;
push @{$self->{'tracks'}}, $track;
}
...
Let your train set be one object, and your tracks be represented by another
class. Keep each as simple and straightforward as possible.
Joseph
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