Chapter 3

Using Class::Struct

Class::Struct

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 exports a single subroutine, struct(), that allows you to build a class 

skeleton with a single subroutine call. You pass the struct() routine information 

about your attributes, and it generates and compiles the code for your new class, 

including a constructor called new() and an accessor mutator for each attribute. 

For example, say you're building a class to manage the scientific probes aboard the 

BOA spacecraft. The BOA::Probe class has a number of attributes that describe an 

individual probe. Here's what the class file looks like using Class::Struct:

package BOA::Probe;

use Class::Struct;

# create accessors and constructor

struct(id       =>  $ ,

       model    =>  $ ,

       contents =>  $ ,

       heading  =>  $ ,

       status   =>  $ );

The struct() call takes a list of key value pairs that describe the names of attributes 

and their types. The preceding class uses the  $  type, which indicates it is scalar. 

This provides the interface you're familiar with the accessor mutator created 

takes zero or one argument and gets or sets its value. After calling struct(), six new 

methods are created one for each of the attributes and a new() method. This 

new() takes a list of key value pairs to initialize the contents of the object. Here's an 

example of how to use the new class:

# create a new probe

my $probe = BOA::Probe >new(id => 10503, model => "BOA Mark 10");

# modify heading and status

$probe >heading([10, 20, 100, 50]);  # heading at (10,20,100) with at 50 kph

$probe >status("moving");

Class::Struct supports more than just scalar attributes. You can specify that an 

attribute will hold an array, a hash, or an object of a specific class. This may seem 

unnecessary the scalar attributes can already hold a reference to any of these 

types but declaring these type allows Class::Struct to generate more powerful 

9. Written by Jim Miner, based on Class::Template by Dean Roehrich. The module is included 

with Perl.

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