How to call a grandparent method in perl - perl

Question

I was recently needing to call the grandparent of a class. Let's say I have:
use strict;
use warnings;
use 5.10.0;
package Superhero;
sub new {
my $class = shift;
return bless {}, $class;
}
sub SaveWorld {
my $self = shift;
my %args = (
hero => "nobody",
#_
);
my $hero = $args{hero};
say "$hero saved the world again";
$self->{status} = "World saved by $hero";
}
sub WorldStatus() {
my $self = shift;
return $self->{status};
}
package Superman;
use parent -norequire, qw(Superhero);
sub SaveWorld {
my $self = shift;
my %args = ( hero => "superman" );
$self->SUPER::SaveWorld(%args);
}
and wanted a new class Spiderman that was like Superman but slightly different:
package Spiderman;
use parent -norequire, qw(Superman);
sub SaveWorld {
my $self = shift;
my $hero = "spiderman";
??? # Call Superhero->SaveWorld
}
for being called as:
my $hero = Spiderman->new;
$hero->SaveWorld();
say $hero->WorldStatus();
It seems quite bad documented how to perform that ??? call.
Something like $self->SUPER::SUPER::SaveWorld($hero) doesn't work (it would look for a package called "SUPER::SUPER").
To make matters worse, the parent itself was dynamic, so a literal $self->Superhero::SaveWorld(%args); was not possible.
The class itself can be easily extracted with my $class = $Superman::ISA[0];, though.
A static call could be achieved with something like:
my $eval = $class . '::SaveWorld($self, %args)';
eval $eval;
which was not working, though (it seems to work as expected in this example, though).

Answer 1

You could use the following:
$self->Superhero::SaveWorld(%args);
Doing so would just compound a broken design. You should fix your design rather than using this. It's unclear what the fix would be because your example makes no sense: A spider man isn't a super man.

Answer 2

The trick is to use a string with the method name.
As found from this answer by Borodin:
my $method = join '::', $class, "SaveWorld";
or just
my $method = "${class}::SaveWorld";
(but note the ${class} to not go over the ::, otherwise it tries ${class::SaveWorld}!)
Thus,
package Spiderman;
use parent -norequire, qw(Superman);
sub SaveWorld {
my $self = shift;
my %args = ( hero => "spiderman" );
my $class = $Superman::ISA[0];
say "I am looking for $class";
my $method = join '::', $class, "SaveWorld";
$self->$method(%args);
}