Below is a very ugly hack that I used some time ago, and that has worked until today, for initial (hard-coded) inheritable class data. I'm sure there is a better way of doing this, and I haven't finished my way through Conway's book yet. The initData method manually "walks" through the @ISA hierarchy in a depth-first fashion, incorporating each class' %DATA hash into the object. So you create an object, call its init method (which calls initData), and it populates the object with the appropriate hashes. So in each package you just have to declare the global %DATA hash containing the initial data

Ugly, I know, but it works. 

#!/usr/local/bin/perl -w

use strict;

package A;

use vars qw(%DATA);

%DATA=('name' => 'A name',
       'data' => 'A data'
      );

sub new {
  my $class=shift;
  my $self={};

  bless $self, $class;
}

sub init {
  my $self=shift;
  my $class=ref($self);
  $self->initData($class);
  # other initialization here
}

sub initData {
  my ($self, $class, $visited)=@_;
  $visited={} unless $visited;
  # First visit all the superclasses
  no strict 'refs';
  foreach my $c (@{"${class}::ISA"}) {
    $self->initData($c, $visited);
  }
  # Now take my own %DATA hash
  if (!exists($visited->{$class})) {
    $self->copyData(%{"${class}::DATA"});
    $visited->{$class}=1;
  }
}

sub copyData {
  my $self=shift;
  my %data=@_;
  $self->{$_}=$data{$_} foreach keys(%data);
}

####################

package B;

use vars qw(@ISA %DATA);

@ISA=qw(A);

%DATA=('name' => 'B name');

1;

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--ZZamboni

In reply to Re: opinions on the best way to inherit class data by ZZamboni
in thread opinions on the best way to inherit class data by d_i_r_t_y

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