Re: Can a class constructor create an instance of a derived class and return it? Or, can objects transmute into other objects?

[Anonymous Monk]

Can a class constructor create an instance of a derived class and return it? Or, can objects transmute into other objects?

Yes, and yes. As long as you document it properly, it's fine. Re-blessing already-blessed objects is a little bit sketchy, but if you know what you're doing, go ahead (that's actually how subclass constructors work in C++). I would tend to write SNMPObject::CiscoStack->new(...) instead of SNMPObject::CiscoStack::new(...) in the superclass constructor, though.

[stevieb]

When I'm doing things like this, I prefer to use a second method aside from new in the parent class to generate the new objects:

sub new {
    return bless {}, shift;
}
sub build {
    my $self = shift;
    my $sub_obj = Other::Class->new;
    push @{ $self->{sub_objects} }, $sub_obj;
    return $sub_obj;
}

That way, the other objects can be injected into a parent object for tracking purposes (ie. it provides a list of all other in-use objects of the sub types. Here's a very basic example.

my $parent = Obj->new;
my $sub_obj_1 = $parent->build;
my $sub_obj_2 = $parent->build;

for (@{ $parent->{sub_objects} }){
    print $_->name . "\n";
}