Objects

 perldoc perltoot
 perldoc perltooc
 perldoc perlobj

What is OO?

• attributes and attribute values -- the data to which an object provides access are known as the object's attribute values. The slots in an object storing those attribute values are called attributes. For example, our ATM object might have an attribute called "id", that holds the unique id number for this ATM. The attribute value for "id" could be "317". It might have another attribute called "available_cash" that holds the total amount of cash left in the machine available for dispensing, and that attribute value could be "$860".
• constructor -- a method in the class that returns a new object. This is how we create objects.
• setter -- a method that sets (writes) some attribute value in an object. For example, our ATM class might have a setter called "set_new_balance_for_customer()" which takes a dollar amount and customer ID as arguments, and sets the new balance for that customer.
• getter -- (sometimes called "accessor") a method that gets (reads) some attribute value in an object. For example, our ATM class might have a getter called "get_account_balance()" which takes a customer ID and returns the account balance for that customer. Another example is a method called "get_available_cash" that returns the available cash for this object.

How do I do OO in Perl?

use strict;
use ATM;

my $atm = ATM->new;  # create new object

$atm->deposit_funds(id => 8, amount => '29.95');

#------------------------------------------------------------------------
# Each Truck object is a blessed hash with attributes like this:
#
# $self = { 
#          make => 'chevy',
#          year => 1995
#         }
#------------------------------------------------------------------------

package Truck;

use strict;

# The constructor method
sub new {
    # Normally $class will be 'Truck' (if you're curious, inheritance 
    # could cause this to change)
    my $class = shift;   
    
    my $self = {};

    bless($self, $class);
    return $self;
}


sub register {
    my ($self, %args) = @_;

    $self->{make} = $args{make};
    $self->{year} = $args{year};
}


# Accessors to get truck make and year

sub get_make {
    my $self = shift;
    return $self->{make};
}

sub get_year {
    my $self = shift;
    return $self->{year};
}

1;

use strict;
use Truck;

# create 2 new Truck objects
my $chevy  = Truck->new;
my $nissan = Truck->new;

# register the Trucks (that is, call the register method on each Truck object)
$chevy->register(make => 'Chevrolet', year => 1995);
$nissan->register(make => 'Nissan', year => 2007);

print "Hi, I have 2 trucks:\n\n";

# iterate over the truck objects and print out their attribute values
foreach my $truck ($chevy, $nissan) {
   my $make = $truck->get_make;
   my $year = $truck->get_year;

   print "One is a $make truck, made in $year\n";
}