Chapter 3

Or if you need a call to your own init() and want to accept an initializer hash, you 

could implement the following:

package BOA::Probe;

use Class::MethodMaker

   new_with_init =>  new ,

   new_hash_init =>  hash_init ,

   get_set       => [ qw(id model contents heading status) ];

# called from the generated new()

sub init {

  my $self = shift;

  $self >hash_init(@_);

  # do other initialization stuff...

}

The method generated by new_hash_init is specially designed to be called as both a 

class method and an object method. Isn't that cool?

Class::MethodMaker sports some truly comprehensive support for list and 

hash attributes, generating common class methods as well as many useful variations 

on the normal accessor mutators. To top it all off, Class::MethodMaker can itself be 

extended using inheritance. For this and more, see the Class::MethodMaker 

documentation.

Visual Modeling

Complex object oriented systems are often easier to design visually than textually. 

The Unified Modeling Language (UML)

12

 specifies a popular notation for doing 

visual design of object oriented systems. There are numerous tools available to aid 

in the task from simple drawing applications to complex software design tools that 

generate code (although they rarely support Perl).

However, in my experience, these tools are usually unnecessary. Visual modeling 

done on a whiteboard or on paper is just as valuable as that done on a computer. 

Seeing your design laid out visually can help clarify your thinking and reveal 

dangerous complexity problems that aren't apparent from your documentation. 

The key to using visual modeling successfully is to keep it simple; don't get caught 

up in trying to represent the entirety of a working system in a diagram.

Figure 3 2 shows a simple UML class diagram of a few of the BOA classes I've 

used as examples earlier. The diagram shows three classes BOA::Logger, 

BOA::Logger::Enhanced, and BOA::Network. The items in the top half of the class 

12. See http://www.uml.org for details.

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