Intermediate Perl

Chapter 11. Introduction to Objects

Object-oriented programming (OOP) helps programmers run code sooner and maintain it easier by organizing the code into things that we can name. We need a little more infrastructure to get going with objects, but in the long run, it’s worth it.

The benefits of OOP become worthwhile when our program (including all external libraries and modules) exceeds about N lines of code. Unfortunately, nobody can agree on what the value of N is, but for Perl programs, it’s arguably around 1,000 lines of code. If our whole program is only a couple hundred lines of code, using objects is probably overkill.

Like references, Perl’s object architecture was grafted on after a substantial amount of existing pre-Perl 5 code was already in use, so we had to ensure that it wouldn’t break existing syntax. Amazingly, the only additional syntax to achieve object nirvana is the method call, introduced shortly. But the meaning of that syntax requires a bit of study, so let’s proceed.

The Perl object architecture relies heavily on packages, subroutines, and references, so if you’re skipping around in this book, please go back to the beginning. Ready? Here we go.

If We Could Talk to the Animals...

Obviously, the castaways can’t survive on coconuts and pineapples alone. Luckily for them, a barge carrying random farm animals crashed on the island not long after they arrived, and the castaways began farming and raising animals.

Let’s listen to those animals for a moment:

sub Cow::speak ...