Inheritance in Perl - perl

Question

I have two classes, one is the base class(Employee) and the other its subclass which inherits it (Extend) the codes of which are shown below :
package Employee;
require Exporter;
our #EXPORT = ("getattr");
our $private = "This is a class level variable";
sub getattr {
print "Inside the getattr function of Employee.pm module \n";
$self = shift;
$attr = shift;
return ($self->{$attr});
}
1;
================
package Extend;
use base qw(Employee);
sub new {
print "Inside new method of Employee.pm \n";
my $class = shift;
my %data = (
name => shift,
age => shift,
);
bless \%data , $class;
}
sub test {
print "Inside test method of Extend class \n";
}
1;
==================
Now I have another piece of code which is using the Extend class :
use Extend;
my $obj = Extend->new("Subhayan",30);
my $value = $obj->getattr("age");
print ("The value of variable age is : $value \n");
$obj->test();
print "Do i get this : $obj.$private \n";
My question is regarding the variable $private defined in the parent class. As per my concept of inheritance attributes and methods of the parent class should be available through the subclass object . For example the function getattr runs fine . But why am I not being able to access $private variable using the base class Extend object .
What am I missing here ? Can someone please help ?

Answer 1

Variables don't get inherited the same way subs do. To access it, you need to specify the entire package name (and yes, when you declare $private, you need our, not my):
print "$Employee::private\n";
It's much more robust to define accessor methods:
# Employee package
sub private {
return $private;
}
...then in your script:
my $var = private();
To inherit object attributes from Employee, you can do:
# Employee
sub new {
my $self = bless {
dept => 'HR',
hours => '9-5',
}, shift;
return $self;
}
# Extend
sub new {
my $class = shift;
my $self = $class->SUPER::new; # attrs inherited from Employee
$self->{extended} = 1;
return $self;
}
# script
my $extend = Extend->new;
Now $extend looks like:
{
dept => 'HR',
hours => '9-5',
extended => 1,
}
You most likely wouldn't set dept or hours in the base class as it will apply to all employees, but I digress.