Advanced OO Perl
Learn about advanced OO Perl.
Creating and using objects in Perl with Moose is easy. Designing good programs is not. It’s as easy to overdesign a program as it is to underdesign it. Only practical experience can help us understand the most important design techniques, but several principles can guide us.
Favor composition over inheritance
Novice OO designs often overuse inheritance to reuse code and exploit polymorphism. The result is a deep class hierarchy with responsibilities scattered all over the place. Maintaining this code is difficult—who knows where to add or edit behavior? What happens when code in one place conflicts with code declared elsewhere? Inheritance is only one of many tools for OO programmers. It’s not always the right tool. It’s often the wrong tool. A Car may extend Vehicle::Wheeled (an is-a relationship), but Car may better contain several Wheel objects as instance attributes (a has-a relationship).
Decomposing complex classes into smaller, focused entities improves encapsulation and reduces the ...