Rating  - good while it lasts
This is a collection of the author's columns of the same name from C++ Report. This is not a tutorial; you need to be familiar with the original patterns from the GoF book, and the more you like C++, the better.
The book takes you through a couple of extended examples, including an abstraction of a Unix-style file system, slowly building up functionality, and demonstrating how to introduce patterns and choose which one to use. If you're looking for some examples of how to use patterns, along the lines of Design Patterns Explained, this is one of the best books you could hope to read. There's also a couple of non-GoF patterns. In particular, the chapter that details some of the discussion between the GoF on the merits of the proposed Multicast pattern is a very illuminating expose of pattern thinking.
While it's unclear who wrote which bit of the original GoF book, from reading Pattern Hatching, it's an enormous pity Vlissides wasn't handed the lion's share of the writing task. Where the GoF book can be stodgy and opaque, Pattern Hatching is informal and conversational. Vlissides clearly had a love of writing, and he gives advice on writing style for patterns in the final chapter.
A caveat is the C++-centric approach of the book. It no doubt made a lot of sense in the context of the original articles in a publication devoted to that language. Non C++ users should be warned that a large chunk of the book considers handling memory management with singleton - you may not find much of value.
And as other reviewers have noted, this is a slim book of 150 pages. If you have to pay more than £10 for it, you probably will feel a bit ripped off.
That said, the material that is here is very good indeed, especially if you're a C++ user. If you can find an affordable copy, you should definitely get it.
Rating  - A great follow-up to the GoF patterns book
John Vlissides, one of the authors of the book that was the germination and incubation of the topic of patterns in computing, once again plucks a golden egg from his fertile imagination. As he states clearly in the introduction, this book is designed as a supplement to the ground- breaking "Design Patterns: Elements of Reusable Object- Oriented Software", commonly referred to as the Gang of Four(GoF) book. The examples in this book are well chosen, and many people will find this book to be a good introduction to the concept of patterns in software construction. The writing in this book is also more fluid than the original design-patterns book.
Exploring software patterns is in many ways a search for the equivalent of the Platonic ideal on forms in philosophy, which is one of the reasons why there is such a cantankerous and sometimes dismissive debate concerning true value of patterns. Chapter 1 is devoted to dealing with some of this, with the bulk of the material being a statement/response to each of the, "Top Ten Misconceptions" concerning software patterns. One point is clear from this chapter, and that is how ill defined the notion of patterns really is. This is not altogether surprising considering how recently the field was conceived, but disturbing because software is such serious stuff. If you wish to become part of the debate, send an email message to patterns-discussions-request@cs.uiec.edu . The body of the message should contain the single word, (without quotes) "Subscribe."
The fundamental topic of chapter 2 is using patterns to design a hierarchical file
system, a topic even computer novices know something about. The first pattern introduced in the solution is composite. Because the context of use is so familiar to anyone who has done serious coding, the definition and purpose of the composite pattern are almost completely clear without having to go to the GoF book. The language of demonstration is C++ and one additional skill that will be very helpful is some knowledge of OMT- style diagrams. Additional GoF patterns used to complete the design of the file system are the proxy, visitor, template, singleton and mediator patterns. There are only 23 patterns in the GoF book, and this "simple" example demonstrates how to use one-forth of them.
Several years ago when I was grinding my way through the GoF book for the first time, I considered the singleton pattern to be the simplest of the 23 listed in the book. The intent of the singleton is extremely simple:
Ensure a class only has one instance, and provide a global point of access.
It seemed almost trivial to understand and implement.
In chapter three, Vlissides presents additional insights into the singleton that serves as a stiff reminder of the following maxim that paraphrases Shakespeare:
There are more things in your patterns sir, than are contained in your concepts
Patterns are dynamic, flexible entities, and we are only beginning to understand the potential benefits and risks inherent in their use. The other patterns expanded upon in the chapter are observer, visitor, and memento. A new pattern, the generation gap, is also introduced.
Chapter four is devoted to the multicast pattern, one that did not appear in the original GoF book. The style of presentation in this case takes us behind the scenes a bit. It points out that establishing the existence of a pattern, like many other things, is based on a bit of constructive chaos.
In Chapter 5, which is the final chapter, the seven habits of effective pattern writers are listed and described in detail. Clearly, the first is most important, although in the modern world of hetic-devolopment schedules, the least one used is: Habit 1: Taking time to reflect.
In closing, this book is without question a significant advancement on the original GoF book, and so well done that beginners can start their study of patterns with it. It may be the best book of patterns that will be published this year.
Published in Journal of Object-Oriented Programming, reprinted with permission.
Rating - Great insights
I liked this book very much, especially the first part, where the usage of some of the GoF patterns is shown in the practical example of designing an OO file system model. Also, it was interesting to read the discussion the GoF had in the time of writing Design Patterns book about Multicast pattern and whether it's a separate pattern or a special case of the Observer.
All in all, quite interesting reading. There's also some useful information for the sofware developers who want to document their own patterns.
The only thing I didn't really like about the book is that it's too short.
Rating - My coments on the book
A very helpful book especially very after GoF?s one reading . However it has a lot of C++ specific places, java developers will find the book also interesting :). It's written by one from the gang - John M. Vlissides. First part of the book gives a glance view of applying several GoF patterns in dummy simple file system building (Composite , Proxy, Visitor, Singleton, Mediator ) . The author also introduces two new patterns which don't mentioned in the Design Pattern (Generation Gap, Multicast ) in the next parts .
Rating  - Interesting, but not a lot of content
This really is the best book I know for describing the process of applying patterns to an application. It's a definite skill, a definite thought process, and very hard to convey. I do it by setting people specific problems to solve with specific patterns and hoping they develop the mapping for themselves. That usually works, sooner or later.
The first half of this book is like sitting behind Vlissides while he works at the keyboard, and listening to him talk to himself. It's very informal and conversational. I don't know how well it generalizes to other patterns in other contexts. For some people, though, a concrete example like this seems very helpful.
The second half of the book didn't give me much useful information. It continues the informal, conversational style. This part, however, involves several developers in the process of identifying, characterizing, and sometimes disqualifying candidates for design-pattern-hood. As much as I respect the people in the conversation, that section has a Disney-like fictional quality that I don't like. The old conversations have been reconstructed and morphed into some cleaned-up and picked-over form that reads well. Mostly, they just don't say anything that I can really use.
Seeing an example worked may help some people. On the whole, though, this book has less information per inch of shelf space than many others. Populate your bookshelf accordingly.
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