Accessing the Instance Data (Learning Perl Objects, References & Modules)

home | O'Reilly's CD bookshelfs | FreeBSD | Linux | Cisco | Cisco Exam

Learning Perl Objects, References & Modules

9.3. Accessing the Instance Data

Because you get the instance as the first parameter, you can now access the instance-specific data. In this case, let's add a way to get at the name:

{ package Horse;
  @ISA = qw(Animal);
  sub sound { "neigh" }
  sub name {
    my $self = shift;
    $$self;
  }
}

Now you call for the name:

print $tv_horse->name, " says ", $tv_horse->sound, "\n";

Inside Horse::name, the @_ array contains just $tv_horse, which the shift stores into $self. It's traditional to shift the first parameter into a variable named $self for instance methods, so stay with that unless you have strong reasons otherwise. Perl places no significance on the name $self, however.[41]

[41]If you come from another OO language background, you might choose $this or $me for the variable name, but you'll probably confuse most other Perl OO-hackers.

Then $self is dereferenced as a scalar reference, yielding Mr. Ed. The result is:

Mr. Ed says neigh.

Library Navigation Links

Copyright © 2003 O'Reilly & Associates. All rights reserved.