#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

{
    package MyApp::Object;
    use Moose;

    has greeting => (isa => 'Str', is => 'ro', required => 1);

    sub collection { ref(shift) . '::Collection' }

    {
        my %collection;
        sub BUILD {
            my ($self) = @_;
            my $class = $self->collection;
            Moose::Meta::Class->create(
                $class,
                methods => {
                    push  => sub { push @{ $collection{ +shift } }, $self },
                    greet => sub {
                        say $_->greeting for @{ $collection{ +shift } }
                    },
                },
            );
            $class->push($self);
        }
    }

    __PACKAGE__->meta->make_immutable;
}

{
    package MyApp::ChildObject;
    use Moose;
    extends 'MyApp::Object';

    __PACKAGE__->meta->make_immutable;
}


my $o = 'MyApp::Object'->new(greeting => 'Hallo');
$o->collection->greet;

my $c1 = 'MyApp::ChildObject'->new(greeting => 'Ciao');
my $c2 = 'MyApp::ChildObject'->new(greeting => 'Salut');
$c1->collection->greet;