comment on

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
[download]

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.

Perl --((8:>*

In reply to Re^2: How to use Inheritance with Inside-Out Classes and Hash Based Classes by Perl Mouse
in thread How to use Inheritance with Inside-Out Classes and Hash Based Classes by ghenry

Are you posting in the right place? Check out Where do I post X? to know for sure.
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
Want more info? How to link or How to display code and escape characters are good places to start.


P is for Practical
	PerlMonks