Design Patterns
Elements of Reusable Object-Oriented Software
Produced by KevinZhang
Design Patterns: Elements of Reusable Object-Oriented Software
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Contents
Preface to CD........................................................5
Preface to Book......................................................7
Foreword.............................................................9
Guide to Readers....................................................10
1 Introduction......................................................11
1.1 What Is a Design Pattern?......................................12
1.2 Design Patterns in Smalltalk MVC...............................14
1.3 Describing Design Patterns.....................................16
1.4 The Catalog of Design Patterns.................................18
1.5 Organizing the Catalog.........................................21
1.6 How Design Patterns Solve Design Problems......................23
1.7 How to Select a Design Pattern.................................42
1.8 How to Use a Design Pattern....................................44
2 A Case Study: Designing a Document Editor.........................46
2.1 Design Problems................................................46
2.2 Document Structure.............................................47
2.3 Formatting.....................................................53
2.4 Embellishing the User Interface................................56
2.5 Supporting Multiple Look-and-Feel Standards....................60
2.6 Supporting Multiple Window Systems.............................64
2.7 User Operations................................................72
2.8 Spelling Checking and Hyphenation..............................77
2.9 Summary........................................................90
Design Pattern Catalog..............................................93
3 Creational Patterns...............................................94
Abstract Factory...................................................99
Builder...........................................................110
Factory Method....................................................121
Prototype.........................................................133
Singleton.........................................................144
Discussion of Creational Patterns..................................153
Design Patterns: Elements of Reusable Object-Oriented Software
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4 Structural Patterns..............................................155
Adapter...........................................................157
Bridge............................................................171
Composite.........................................................183
Decorator.........................................................196
Façade............................................................208
Flyweight.........................................................218
Proxy.............................................................233
Discussion of Structural Patterns.................................246
5 Behavioral Patterns..............................................249
Chain of Responsibility...........................................251
Command...........................................................263
Interpreter.......................................................274
Iterator..........................................................289
Mediator..........................................................305
Memento...........................................................316
Observer..........................................................326
State.............................................................338
Strategy..........................................................349
Template Method...................................................360
Visitor...........................................................366
Discussion of Behavioral Patterns.................................382
6 Conclusion.......................................................388
6.1 What to Expect from Design Patterns...........................388
6.2 A Brief History...............................................392
6.3 The Pattern Community.........................................393
6.4 An Invitation.................................................395
6.5 A Parting Thought.............................................396
A Glossary.........................................................397
B Guide to Notation................................................404
B.1 Class Diagram.................................................404
B.2 Object Diagram................................................406
B.3 Interaction Diagram...........................................407
C Foundation Classes...............................................409
C.1 List..........................................................409
C.2 Iterator......................................................412
C.3 ListIterator..................................................413
Design Patterns: Elements of Reusable Object-Oriented Software
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C.4 Point.........................................................413
C.5 Rect..........................................................414
Bibliography.......................................................416
Design Patterns: Elements of Reusable Object-Oriented Software
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Preface to CD
As we were writing Design Patterns, we knew the patterns we weredescribing had
value because they had proven themselves in manydifferent contexts. Our hope was
that other software engineers wouldbenefit from these patterns as much as we had.
Now, three years after its debut, we find ourselves both grateful andthrilled
by how the book has been received. Lots of people use it.Many tell us the patterns
have helped them design and build bettersystems. Many others have been inspired
to write their own patterns,and the pool of patterns is growing. And many have
commented on whatmight be improved about the book and what they would like to
see inthe future.
A recurring comment in all the feedback has been how well-suited thebook is to
hypertext. There are numerous cross-references, andchasing references is
something a computer can do very well. Sincemuch of the software development
process takes place on computers, itwould be natural to have a book like ours
as an on-line resource.Observations like these got us excited about the potential
of thismedium. So when Mike Hendrickson approached us about turning the bookinto
a CD-ROM, we jumped at the chance.
Two years and several megabytes of e-mail later, we're delighted thatyou can
finally obtain this edition, the Design Patterns CD,and put its unique capabilities
to work. Now you can access a patternfrom your computer even when someone has
borrowed your book. You can search the text for key words and phrases. It's also
considerably easier to incorporate parts of it in your own on-line
documentation.And if you travel with a notebook computer, you can keep the
bookhandy without lugging an extra two pounds of paper.
Hypertext is a relatively new publishing venue, one we arelearning to use just
like everyone else. If you have ideas on howto improve this edition, please send
them todesign-patterns-cd@cs.uiuc.edu.If you have questions or suggestions
concerning the patternsthemselves, send them to
thegang-of-4-patterns@cs.uiuc.edumailing list. (To subscribe, send e-mail to
gang-of-4-patterns@cs.uiuc.eduwith the subject "subscribe".) This list has quite
a few readers, and many of them can answer questions as well as we can—andusually
a lot faster! Also, be sure to check out thePatterns Home Page
athttp://hillside.net/patterns/.There you'll find other books and mailing lists
on patterns, notto mention conference information and patterns published on-line.
This CD entailed considerable design and implementation work. We areindebted to
Mike Hendrickson and the team at Addison-Wesley for theiron-going encouragement
and support. Jeff Helgesen, Jason Jones, andDaniel Savarese garner many thanks
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