thoughts of a doug

package Node;
 
use Moose 0.89;
 
has child => (
  is  => 'rw',
  isa => 'Node',
  clearer   => 'clear_child',
  predicate => 'has_child',
  trigger   => \&_child_trigger,
);
has parent => (
  is  => 'rw',
  isa => 'Node',
  clearer   => 'clear_parent',
  predicate => 'has_parent',
);
 
before clear_child => sub {
  my ($self) = @_;
 
  # Trigger dissociate the parent from the child about to be cleared
  $self->_child_trigger(undef, $self->child);
 
  return;
};
 
sub _child_trigger {
  my ($self, $child, $previous_child) = @_;
 
  if (defined $previous_child) {
    # Remove this node as the parent of the previous child
    $previous_child->clear_parent();
  }
 
  if (defined $child) {
    # Set this node as the parent of the new child
    $child->parent($self);
  }
 
  return;
}
 
no Moose;
 
1;