Object Oriented Perl

chromatic has brought us yet another pithy programming-book review, this time of Damien Conway's Object Oriented Perl. This sounds like a good book for those interested in not only an overview, but a book that pushes them into at least a few practical applications -- but not one too intimidating to learn from.

Object Oriented Perl author Damian Conway pages 490 publisher Manning Publications, 09/1999 rating 10 reviewer chromatic ISBN http://www.thinkgeek summary Damian Conway demonstrates the elegance of Object Oriented programming in Perl, exposing the flexibility and ingenuity of itsdesign

The Scoop A few common myths sully Perl's reputation in the Object Oriented world: Some claim the functionality is tacked on, while others insist that it is insecure, impure, and obscure. Damian Conway handily dispels these rumors in a gem of a book. Though occasionally delving into black magic, Object Oriented Perl is still accessible to novices. Paraphrasing the preface, this book might very well "[lower] cholesterol... [promote] world peace" -- for wizards and initiates alike. (Or at least raise their skills another level.) The Lowdown The starting point is an introduction to objects and the basic theory behind the OO discipline. This serves as a good overview of the first portion of the book. Following closly is an impressive thirty-page introduction to Perl. As newbies would shortly be overwhelmed, it is not intended as a first look at the language. Rather, it fills in the gaps left by an eclectic education. The chapter ends with a whirlwind tour of more advanced (read, underused) techniques, including the best typeglob discussion I've ever read.

Subsequent chapters narrow the focus and intensify the explanation. Conway first introduces three simple rules of Perl objects: classes are packages; methods are subroutines; and objects are blessed referents. While some forks of the trail are quite exotic (blessing a regular expression into an object?), they're all entertaining and very informative.

Programmatic examples follow an iterative and interactive development process, as is common in technical books. The author states a problem and then writes some initial code using a newly explained feature. Refining the program, he demonstrates other ways of achieving the same goal with less code, more features, and better style. Most examples are creative and fairly easily understood (a CD tracking system, a network model), though some, built from computer-science type examples (a pretty printer, a lexer), may be too esoteric for some readers.

As befitting the Perl philosophy, Conway is not hesitent to break with OO tradition as expressed in languages such as C++, Java, Smalltalk, or Eiffel. (Appendix B discusses language features of each with regard to Perl in compact but enlightening technical fashion.) There's an overwhelming sense of Perlishness about the whole thing, and that shines through on every page. Expect to exploit the language's flexibility to achieve amazing results.

By the end of chapter seven, you'll know everything you really need to know to be an effective and productive OO Perl hacker. Luckily, the increasingly specialized information in the last few chapters is optional. You may never use it, but you'll be better for it. As the most extreme example, the Multiple Dispatch chapter explores three rather exotic approaches I've never seen in a Perl program before (dynamic dispatch tables -- armed with this, you could probably write a window manager in Perl). For the paranoid or the purist, a chapter on encapsulation turns Perl's normally lenient access mechanisms around, protecting data through scalars and secure hashes.

The Summary Superbly organized and excellently explained, this is the definitive book on Object Oriented programming with Perl. Judging from the comments of more qualified experts, we agree that this book belongs on the shelf of any serious Perl hacker. Purchase this book at ThinkGeek. Table of Contents

1. What you need to know first (an object-orientation primer)
2. What you need to know second (a Perl refresher)
3. Getting started
4. Blessing arrays and scalars
5. Blessing other things
6. Inheritance
7. Polymorphism
8. Automating class creation
9. Ties
10. Operator overloading
11. Encapsulation
12. Genericity
13. Multiple Dispatch
14. Persistent objects

Appendices

1. Quick reference guide
2. What you might know instead

Comments

An excellent Perl book - with one proviso

[Ars-Fartsica]

I highly recommend this book to anyone who is (or thinks they are) a real perl-head. You will undoubtably learn something new about the language.

My proviso is this - if you really are interested in object-oriented programming (moreso than simply being a way to write perl, but interested in the methodology itself), then you may want to try Python or another langauge. Perl folks are historically very defensive and perhaps insecure about their OO implementation - Advanced Perl Programming spends chapters explaining to great (and convoluted) pains how Perl's OO approach is superior...but like in Conway's book, you get the notion that it is an apologistic stance.

Don't get me wrong, I love perl and was on the advance list to get Conway's book. While I have my misgivings about OO Perl, this is still a great Perl book and belongs next to the Camel book on any serious PerlMonk's shelf.