Learning how to use inheritance...

[kiat]

Hi Monks,

I found some oo perl example code to show how inheritance works. The following is the code in its originality:

#!/usr/local/bin/perl -w

package One;

sub new {
   $class = shift;
   print "creating object of class $class\n";
   bless {}, $class;
}


package Two;

@ISA = ("One");

sub new {
   $class = shift;
   print "creating object of class $class\n";
   bless {}, $class;
}

$one = One->new();
$two = Two->new();

Since there are two package names One and Two (corresponding to two classes), I'll need to save 'package One' as One.pm and 'package Two' as 'Two.pm'.

My question is, shouldn't there be a third file (one that's named say main.pl ?) that is being called when one executes the program? In order words, do I need to create a third file (shown below) in addition to the two pm files:

# main.pl
use One;
use Two;

$one = One->new();
$two = Two->new();

# So, to execute the program, I type
>perl main.pl

Another question I've is: What difference does '@ISA = ("One");' in Two.pm make? I mean there's still a need to declare 'use One' in main.pl before it will execute. When I comment out '@ISA = ("One");' in Two.pm, the code still runs.

I'm new to perl oo so please forgive my rather elementary questions ;)