package MyCollection; use MooseX::Role::Parameterized; parameter type => ( isa => 'ClassName', required => 1, ); parameter attr => ( isa => 'Str', required => 1, ); role { my $p = shift; my ($type, $attr) = ($p->type, $p->attr); has $attr => ( is => 'rw', isa => "HashRef[$type]", traits => ['Hash'], defaults => sub { {} } ); method "summon_$attr" => sub { my $self = shift; foreach my $item (values %{ $self->$attr }) { $item->summon if $item->does('Summonable'); } }; }; # and we'll use MooseX::Declare syntax for the rest... role Summonable { requires 'name'; method summon { say "Come here, ", $self->name; } } class Child with Summonable { has name => ( is => 'ro', isa => 'Str' ); } class Parent { with MyCollection => { type => 'Child', attr => 'children' }; } my $me = Parent->new; $me->children->{isabel} = Child->new(name => 'Isabel'); $me->children->{elliott} = Child->new(name => 'Elliott'); $me->summon_children;