docdurdee has asked for the wisdom of the Perl Monks concerning the following question:

Dearest Monks, I use Math::Vector::Real with XS (I'll refer to it as MVR) as a core dependency of my molecular object system. MVR exports the function V that creates the MVR object (a vector of numbers that has useful methods). e.g. atomic coordinates are MVR objects. My classes use the methods of MVR within a Role. Instances of my classes use the V function: 
my $atom = Atom->new(Z=> 80, coords => [V(0,0,0), V(1,1,1), V(2,2,2)])
+;

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creates a mercury atom with three MVR coordinates. The coords attribute is an ArrayRef-MVR with Array traits; I push_coords, get_coords, set_coords etc. I have two goals: 1. be able to use MVR's V function without having to add use Math::Vector::Real to every script. 2. be able to add MooseX::Storage capabilities for MVR to my classes. So I'm trying to subclass MVR: 
package MyMVR;
#ABSTRACT: Moose subclass of Math::Vector::Real
use 5.008;
use Moose;
use namespace::autoclean;
use MooseX::NonMoose;
use MooseX::Storage;
with Storage ('io' => 'StorableFile' );
extends 'Math::Vector::Real';


__PACKAGE__->meta->make_immutable;

1;

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now using MVR->new works, 
use MyMVR;

my $a = MyMVR->new(0,0,0);
my $b = MyMVR->new(1,1,1);

print $_ ."\n" foreach (@{$a - $b});

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with Moose warnings (that make sense) about MyMVR's new: "The new() method for MyMVR expects a hash reference or a key/value list. You passed an odd number of arguments at MyMVR_test.pl". The V function is no longer accessible. Any help achieving either goal is greatly appreciated! D

Replies are listed 'Best First'.
Re: subclassing Math::Vector::Real with MooseX::NonMoose
by tobyink (Canon) on Sep 12, 2013 at 14:47 UTC

    Firstly, Moose defaults to instances being blessed hashes; MVR seems to used blessed arrayrefs. So use MooseX::NonMoose::InsideOut instead of plain MooseX::NonMoose.

    Secondly, you probably want to write a FOREIGNBUILDARGS method for your class. This translates the arguments passed to your class' constructor into a list of argument that the parent class' constructor expects.

    Lastly, if you want to use this V function, then you'll need to import it into each namespace where you're using it:

    use Math::Vector::Real qw(V);

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    use Moops; class Cow :rw { has name => (default => 'Ermintrude') }; say Cow->new->name
    /div
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      quickly adding this and MX::Nonmoose::InsideOut to MyMVR: 
      sub FOREIGNBUILDARGS { return @{$_[2]}}

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      @_ is (class, key (vec), and value (arrayref)) from the adjusted script: 
      use MyMVR;

my $a = MyMVR->new(vec=>[0,0,0]);
my $b = MyMVR->new(vec=>[1,1,1]);

print $_ ."\n" foreach (@{$a - $b});
print $a->dist($b) . "\n";

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      which works. Thanks!
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[d/l]
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Re: subclassing Math::Vector::Real with MooseX::NonMoose
by salva (Canon) on Sep 12, 2013 at 15:44 UTC
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      Good to know. I'm not sure I understand why yet, so I'll come back to the storage issue later. Thanks Salva.
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