Mark GrandBrad Merrill

Visual Basic

Design Patterns

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Visual Basic Design Patterns

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Mark GrandBrad Merrill

Visual Basic

Design Patterns

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Visual Basic Design Patterns

Published byWiley Publishing, Inc.10475 Crosspoint BoulevardIndianapolis, IN 46256www.wiley.com

Copyright 2005 by Wiley Publishing, Inc., Indianapolis, Indiana

Published simultaneously in Canada

ISBN-13: 978-0-471-26860-4ISBN-10: 0-471-26860-7

Manufactured in the United States of America

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No part of this publication may be reproduced, stored in a retrieval system or transmittedin any form or by any means, electronic, mechanical, photocopying, recording, scanning orotherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copy-right Act, without either the prior written permission of the Publisher, or authorizationthrough payment of the appropriate per-copy fee to the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 646-8600. Requests to thePublisher for permission should be addressed to the Legal Department, Wiley Publishing,Inc., 10475 Crosspoint Blvd., Indianapolis, IN 46256, (317) 572-3447, fax (317) 572-4355, oronline at http://www.wiley.com/go/permissions.

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Library of Congress Cataloging-in-Publication Data:Grand, Mark.Visual Basic design patterns / Mark Grand, Brad Merrill.

p. cm.Includes bibliographical references and index.ISBN-13: 978-0-471-26860-4 (paper/website)ISBN-10: 0-471-26860-7 (paper/website)1. Microsoft Visual BASIC. 2. BASIC (Computer program language) 3. Software patterns.I. Merrill, Brad. II. Title. QA76.73.B3G683 2005005.2'768--dc22

2005007862

Trademarks: Wiley and the Wiley logo are trademarks or registered trademarks of JohnWiley & Sons, Inc. and/or its affiliates, in the United States and other countries, and maynot be used without written permission. Visual Basic is a registered trademark of MicrosoftCorporation in the United States and/or other countries. All other trademarks are the prop-erty of their respective owners. Wiley Publishing, Inc., is not associated with any product orvendor mentioned in this book.

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www.wiley.com

About the Authors

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Mark Grand is an Atlanta-based consultant specializing in Distributed Systems Object Oriented Design and Java. He was the architect of the first commercial B2B e-commerce product for the Internet. Prior to his involvement with Java, Mark spentover 11 years as a designer and implementer of 4GLs. His most recent role in that veinwas as the architect and project manager for an electronic data interchange product.Mark has worked with a number of MIS organizations in capacities such as SoftwareArchitect, Database Architect and Network Designer.

Mark has been involved with object-oriented programming and design since 1982and is now most widely known for his best-selling patterns books. Mark has taught forU.C. Berkeley, Sun and other organizations. You can find more information aboutMark Grand at http://www.markgrand.com/.

Brad Merrill currently works as a software engineer on the ASP.NET team atMicrosoft. Hes previously worked as a .NET technology evangelist at Microsoft, andas a software engineer at Sybase and Digital Equipment Corporation. His areas of expertise are in distributed systems, transaction processing, operating systems, and compiler technology. Brad lives in Redmond, Washington, and is an avid tourna-ment chess player and bridge player. He can be reached at zbrad@cybercom.net orhttp://www.cybercom.net/~zbrad.

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Executive EditorRobert M. Elliott

Development EditorsEmilie HermanEileen Bien CalabroAmi Frank Sullivan

Technical EditorsBrad AbramsGeoffrey MrozRod Stephens

Production EditorAngela Smith

Copy EditorFoxxe Editorial Services

Editorial ManagerMary Beth Wakefield

Vice President & Executive GroupPublisher

Richard Swadley

Vice President and PublisherJoseph B. Wikert

Project CoordinatorErin Smith

Graphics and Production SpecialistsApril FarlingCarrie A. FosterDenny Hager Stephanie D. Jumper

Quality Control TechniciansLeeann HarneyJessica KramerJoe NiesenBrian H. Walls

Proofreading and IndexingJohnna Van HooseTECHBOOKS Production Services

Credits

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About the Authors v

Credits vii

Introduction xxiiiA Brief History of Patterns xxivOrganization of this Book xxivDescription of Patterns xxv

Pattern Name xxviSynopsis xxviContext xxviForces xxviSolution xxviImplementation xxviConsequences xxvii.NET Usage xxviiCode Example xxviiRelated Patterns xxvii

Who Should Read this Book xxviiWhats on the Companion Web Site xxviii

Chapter 1 Overview of UML 1Class Diagram 2Collaboration Diagram 14Statechart Diagram 22

Chapter 2 The Software Life Cycle 25Case Study 28

Business Case 28Define Requirements Specification 29

Contents

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Develop High-Level Essential Use Cases 30Object-Oriented Analysis 32Object-Oriented Design 34

Chapter 3 Fundamental Design Patterns 45Delegation (When Not to Use Inheritance) 47

Synopsis 47Context 47Forces 50Solution 51Implementation 51Consequences 52.NET Usage 52Code Example 52Related Patterns 54

Interface 55Synopsis 55Context 55Forces 56Solution 56Implementation 56

Delegates 57Constructors 57

Consequences 58.NET Usage 58Code Example 58Related Patterns 59

Abstract Base Class 61Synopsis 61Context 61Forces 62Solution 63

AbstractBaseclass 63ConcreteClass1, ConcreteClass2, . . . 64

Implementation 64Consequences 64.NET API Usage 64Code Example 64Related Patterns 67

Interface and Abstract Class 69Synopsis 69Context 69Forces 69Solution 69Consequences 70.NET API Usage 70Code Example 71Related Patterns 72

x Contents

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Immutable 75Synopsis 75Context 75Forces 76Solution 76Implementation 77Consequences 79.NET API Usage 79Code Example 79Related Patterns 80

Proxy 81Synopsis 81Context 81Forces 82Solution 82Implementation 83Consequences 83Code Example 83Related Patterns 91

Chapter 4 Creational Patterns 93Factory Method 95

Synopsis 95Context 95Forces 97Solution 97Implementation 99

Class Determination by Configuration 99Data-Driven Class Determination 100

Consequences 101.NET API Usage 101Code Example 102Related Patterns 107

Abstract Factory 109Synopsis 109Context 109Forces 110Solution 111Implementation 113Consequences 113Code Example 114Related Patterns 119

Builder 121Synopsis 121Context 121Forces 124Solution 124

Contents xi

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Implementation 126The Build Process 126

Consequences 127.NET API Usage 128Code Example 128Related Patterns 129

Prototype 131Synopsis 131Context 131Forces 132Solution 132Implementation 133Consequences 134.NET API Usage 135Code Example 135Related Patterns 139

Singleton 141Synopsis 141Context 141Forces 142Solution 142Implementation 143

Concurrent GetInstance Calls 144Consequences 145.NET API Usage 145Code Example 146Related Patterns 147

Object Pool 149Synopsis 149Context 149Forces 151Solution 152

Reusable 153Client 153ReusablePool 154

Implementation 154Hiding the Object Pool 154Delegating Object Creation 155Ensuring a Maximum Number of Instances 155Data Structure 155Limiting the Size of the Pool 155Managing Stateful Objects 156

Consequences 156Code Example 156Related Patterns 161

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Chapter 5 Partitioning Patterns 163Filter 165

Synopsis 165Context 165Forces 166Solution 166Implementation 169Consequences 170.NET API Usage 170Code Example 170Related Patterns 174

Composite 175Synopsis 175Context 175Forces 177Solution 177Implementation 179Consequences 179.NET Usage 180Code Example 180Related Patterns 185

Read-Only Interface 187Synopsis 187Context 187Forces 189Solution 189Implementation 190Consequences 191Code Example 191Related Patterns 192

Chapter 6 Structural Patterns 193Adapter 195

Synopsis 195Context 195Forces 196Implementation 198Consequences 199Code Example 199Related Patterns 204

Iterator 205Synopsis 205Context 205Forces 206Solution 206

Contents xiii

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