Store a Moose object that has a PDL as an attribute

I am new to Moose and doing quite well until I have hit a snag using a PDL as a property. I want to be able to write an object to a file (I have been using use MooseX::Storage; with Storage('io' => 'StorableFile');, and this object has a PDL as a attribute. PDL::IO::Storable provides the necessary methods to use Storable in this way, however I am at a loss as to how to do this in Moose.

Here is an example, it is a little long, I know, but it is as minimal as I can make it:

#!/usr/bin/perl

package LinearPDL;
use Moose;

use PDL::Lite;
use PDL::IO::Storable;

use MooseX::Storage; 
with Storage('io' => 'StorableFile');

has 'length' => (is => 'ro', isa => 'Num', required => 1);
has 'divisions' => (is => 'ro', isa => 'Int', required => 1);
has 'linear_pdl' => (is => 'ro', isa => 'PDL', lazy => 1, builder => '_build_pdl');

sub _build_pdl {
  my $self = shift;

  my $pdl = $self->length() / ( $self->divisions() - 1 ) * PDL::Basic::xvals($self->divisions());

  return $pdl;
}

no Moose;
__PACKAGE__->meta->make_immutable;

use strict;
use warnings;

my $linear_pdl = LinearPDL->new('length' => 5, 'divisions' => 10);
print $linear_pdl->linear_pdl;

$linear_pdl->store('file'); # blows up here!

my $loaded_lpdl = load('file');
print $loaded_lpdl->linear_pdl;

I think I may have to make a PDL type or perhaps even wrap PDL into something (using MooseX::NonMoose::InsideOut), but perhaps someone can save me from that (or point me down the right road if it is).

Solution

You don't say what actually goes wrong. At a guess you'll need to tell MooseX::Storage how to handle the PDL object using the PDL object's Storable hooks. The documentation for this feature in MooseX::Storage is very poor but MooseX::Storage::Engine has a add_custom_type_handler() method that takes a typename (PDL in your case) and a HashRef of handlers.

MooseX::Storage::Engine->add_custom_type_handler(
    'PDL' => (
        expand   => sub { my ($data) = @_;   ...  },
        collapse => sub { my ($object) = @_; ...  },
    )
);

Please swing past #moose on irc.perl.org or the Moose mailing list and ask.

[Edit: Update with an example based on the tests.]