Web Standards Programmer's Reference: HTML, CSS, JavaScript®, Perl, Python®, and PHP

25.11. Objects

Perl has robust support for object data types. Although a full description of object-oriented programming is beyond the scope of this book, the following sections provide a primer on Perl's handling of objects.

25.11.1. Perl's Object Nomenclature

As with all things Perl, there are several ways (and related syntax) to achieve a desired goal. In this case, there are several ways to work with objects. We will stick with the standard -> separator syntax familiar to most object-oriented programmers.

This syntax uses -> to separate objects and methods. For example, when creating a new object of class dog, you use the new() method similarly to the following:

doberman = dog_object->new();

Object properties are assigned using the associative assignment operator, =>. This creates the properties as hashes (associative arrays) and has the benefit of providing a ready-made method for accessing property values using simple statements such as the following:

print %{doberman}->{'color'};

25.11.2. Perl Constructors

One easy way to create constructors is to use a separate namespace in Perl to create a new() function and associated initialization routines. For example, to create a constructor for the dog class, you could use code similar to the following:

package dog_object;
  sub new {

    my $class = shift;
    my %params = @_;

    bless {
      "color"  => $params{"color"},
      "size"   => $params{"size"}
    }, $class;

  }

This code defines a new namespace (dog_object) where the new() function can be initialized ...