is based on the idea that there are only so many design problems in computer programming. This book identifies some common program-design problems--such as adapting the interface of one object to that of another object or notifying an object of a change in another object's state--and explains the best ways (not always the obvious ways) that the authors know to solve them. The idea is that you can use the authors' sophisticated design ideas to solve problems that you often waste time solving over and over again in your own programming.
The authors have come up with some ingenious ways to solve some common vexations among object-oriented programmers. Want to build a page-layout program that embeds inline images among characters of various sizes? How about building a program that converts files of one format to another? Chances are, some programmer already has thought of a better solution than you will and the recipes you need are here. Solutions are presented in generalised diagrams of data and logic structures. The idea is that you can take the concepts presented here and adapt them--in whatever language you use--to your individual situation. You may have to read some of the chapters several times before you fully understand them, but when you find a solution in this book, it will make your job easier and your results more elegant. --Jake Bond
From the Back Cover
Capturing a wealth of experience about the design of object-oriented software, four top-notch designers present a catalog of simple and succinct solutions to commonly occurring design problems. Previously undocumented, these 23 patterns allow designers to create more flexible, elegant, and ultimately reusable designs without having to rediscover the design solutions themselves.
The authors begin by describing what patterns are and how they can help you design object-oriented software. They then go on to systematically name, explain, evaluate, and catalog recurring designs in object-oriented systems. With Design Patterns as your guide, you will learn how these important patterns fit into the software development process, and how you can leverage them to solve your own design problems most efficiently.
Each pattern describes the circumstances in which it is applicable, when it can be applied in view of other design constraints, and the consequences and trade-offs of using the pattern within a larger design. All patterns are compiled from real systems and are based on real-world examples. Each pattern also includes code that demonstrates how it may be implemented in object-oriented programming languages like C++ or Smalltalk.