Chapter 2

Object Vocabulary

Object oriented (OO) programming has a language all its own. Fortunately for us, 

Perl provides a simple translation from the OO lexicon to everyday Perl.

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 See 

Table 2 2 for a cheat sheet. Don't worry if this vocabulary isn't immediately clear, 

I'll provide more explanation as we go.

Table 2 2. OO Vocabulary Cheat Sheet

OO

Perl

Class

Package

Object

A reference blessed into a package

Method

A subroutine in a class

Object method

A method that expects to be called using an object

Class method

A method designed to be called using a class

Constructor

A class method that returns a new object

Using OO Modules

Before I show you the details of creating an OO module, it helps to know how to use 

one. Here's an example using IO::File, an OO wrapper around Perl's file operators 

(open, print, seek, and so on) included with Perl:

use IO::File;

# create a new IO::File object for writing "file.txt"

my $filehandle = IO::File >new(">file.txt");

# print to the file

$filehandle >print("This line goes into file.txt\n");

# close the file

$filehandle >close();

The three subroutine calls new(), print() and close() are examples of method 

calls. Method calls are the bread and butter of object oriented programming, and 

in typical Perl fashion, there's more than one way to do it. The preceding example 

12. Which is not the case for all those C programmers learning C++ they don't have a leg to 

stand on!

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