You just hit the problem with inheritance - you're extending the class, which means you're tied to its implementation details.
With traditional, hash-based objects, you are right. And that's true for most of the implementations based on a Class::* module of CPAN, including Class::Std as well. And even the new inside out based class being promoted here on Perlmonks last week.
But the pure, not on a module depending, inside-out technique deals with inheritance perfectly. It can inherit from any implementation - and if inherited from, the inheritee can use whatever implementation it wants as well. Of course, if A inherits from B, B inherits from C, and B is using an inside-out technique, but A and C don't, C might still dictate how A is implemented.
#!/usr/bin/perl
use strict;
use warnings;
package HashBased;
sub new {
my $class = shift;
return bless {@_}, $class;
}
sub noise {
my $self = shift;
printf "The %s goes %s!\n", $self->{name}, $self->{sound}
}
sub name {
my $self = shift;
return $self->{name};
}
package InsideOut; {
use Scalar::Util 'refaddr';
my %legs;
our @ISA = 'HashBased';
sub new {
my $class = shift;
my $legs = pop;
my $obj = bless $class->SUPER::new(@_), $class;
$legs{refaddr $obj} = $legs;
return $obj;
}
sub show_legs {
my $self = shift;
printf "The %s has %d legs\n", $self->name, $legs{refaddr $sel
+f};
}
sub DESTROY {
my $self = shift;
delete $legs{$self}
}
}
package main;
my $dog = InsideOut->new(name => 'dog', sound => 'bark', 4);
my $bird = InsideOut->new(name => 'bird', sound => 'peep', 2);
$dog->noise;
$dog->show_legs;
$bird->noise;
$bird->show_legs;
__END__
The dog goes bark!
The dog has 4 legs
The bird goes peep!
The bird has 2 legs
As you can see, the super class is using hash-based objects. But that doesn't prevent an inside-out based class to inherit from it. And you could even inherit from that class and use a hash-based implementation if you want to do so.
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