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use of Universal superclass
this example from a Well House Consultants training course
More on this [link]

This example is described in the following article(s):
   • Learning Object Orientation in Perl through bananas and perhaps Moose - [link]

Source code: B6.pl Module: P310

{
use strict;

package Banana;
use Time::Local;

sub new {
        my ($class,$d,$m,$y,$paid,$q) = @_;
        my %info;
        $info{"date"} = timegm(0,0,12,$d,$m-1,$y);
        $info{"paid"} = $paid;
        $info{"quantity"} = $q;
        bless \%info,$class;
        }

sub getpriceeach {
        my ($which) = @_;
        $which->{"paid"} / $which->{"quantity"};
        }

sub getwhen{
        my ($which) = @_;
        my $lt = localtime($which->{"date"});
        $lt =~ s/\d+:\d+:\d+\s//; # Strip out time
        return $lt;
        }
}

{
use strict;
package LargeBanana;; # sold "each" ... inherit "getpriceeach" from Banana
our @ISA = qw(Banana);
}

{
use strict;
package BestBanana;
our @ISA = qw(Banana);

sub getpriceeach { # sold per kg; 7 bananas in a kg
        my ($which) = @_; # override "getpriceeach"
        $which->{"paid"} / $which->{"quantity"} / 7 ;
        }
}

{
use strict;
package SmallBanana;
our @ISA = qw(Banana);

sub getpriceeach { # these come wrapped in 10s !!
        my ($which) = @_; # override "getpriceeach"
        $which->{"paid"} / $which->{"quantity"} / 10 ;
        }
}

$sept = new SmallBanana (7,9,2010,1.60,1);
$oct = new BestBanana (14,10,2010,1.75,1.4);
$nov = new LargeBanana (5,11,2010,1.80,8);
$dec = "Minced Pie and Custard";
$jan = new BestBanana (6,1,2011,1.65,1.35);

@breakfast = ($sept, $oct, $nov, $dec, $jan);

foreach $item(@breakfast) {

        # isa method in universal superclass lets you work out if an object
        # is something or inherits from it.
        if ($item->isa("Banana")) {
                $pr = $item->getpriceeach();
                print "price of this item (each) is $pr\n";
        } else {
                print "Cannot work out price each\n";
        }

        # can will tell you if an object supports a method
        if ($item->can("getwhen")) {
                $pr = $item->getwhen();
                print "Purchased $pr\n";
        } else {
                print "Unknown purchase date\n";
        }

        # IMPORTANT WARNING ... if you find yourself using these a lot you
        # probably have GOT THE DESIGN WRONG! You should be using polymorphism
        # to do this lot!

}

__END__

munchkin:pl grahamellis$ perl B6.pl
price of this item (each) is 0.16
Purchased Tue Sep 7 2010
price of this item (each) is 0.178571428571429
Purchased Thu Oct 14 2010
price of this item (each) is 0.225
Purchased Fri Nov 5 2010
Cannot work out price each
Unknown purchase date
price of this item (each) is 0.174603174603175
Purchased Thu Jan 6 2011
munchkin:pl grahamellis$

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