《基元设计模式(英文版)/Jolt大奖精选丛书》编著者史密斯。

本书介绍了一类全新的设计模式，称为基元设计模式(Elemental Design Pattem)，其为软件工程设计模式的研究和应用打下了基础。基元设计模式深深植根于软件程序设计理论的研究，但其目的却在于实践性和实用性。从程序设计的新手，到资深的开发工程师，都是基元设计模式的目标受众。它能够带领学生加入软件工业的大军，也能够为研究者打开新的思路。

《基元设计模式(英文版)/Jolt大奖精选丛书》编著者史密斯。

即使是经验丰富的软件专业人士，也会发现要为其企业找到能带来实质价值的模式应用方式殊非易事。《基元设计模式(英文版)/Jolt大奖精选丛书》首次以全面的方法论介绍基元设计模式，给出标准的命名和描述，阐述它们的重要性，帮助人们比较和选用，充分利用模式的真正力量，将它们转化成实际的、更加简洁直接的软件实现，并得到非常不错的效果。

1 Introduction to Design Patterns 1

1.1 Tribal Musings 5

1.2 Art or Science? 9

1.2.1 Viewing Patterns as Rote 9

1.2.2 Language-Dependent Views 10

1.2.3 From Myth to Science 12

2 Elemental Design Patterns 13

2.1 Background 14

2.2 The Where, the Why, the How 17

2.2.1 Decomposition of Decorator 18

2.2.2 Down the Rabbit Hole 21

2.2.3 Context 30

2.2.4 The Design Space 33

2.3 Core EDPs 42

2.4 Conclusion 44

3 Pattern Instance Notation 45

3.1 Basics 45

3.2 The PINbox 49

3.2.1 Collapsed PINbox 49

3.2.2 Standard PINbox 51

3.2.3 Expanded PINbox 55

3.2.4 Stacked PINboxes and Multiplicity 56

3.2.5 Peeling and Coalescing 62

3.3 Conclusion 65

4 Working with EDPs 67

4.1 Composition of Patterns 68

4.1.1 Isotopes 72

4.2 Recreating Decorator 77

4.3 Refactoring 91

4.4 The Big Picture 101

4.5 Why You May Want to Read the Appendix 105

4.6 Advanced Topics 108

4.6.1 Focused Documentation and Training 108

4.6.2 Metrics 109

4.6.3 Procedural Analysis 112

4.7 Conclusion 112

5 EDP Catalog 115

Create Object 117

Retrieve 126

Inheritance 130

Abstract Interface 140

Delegation 145

Redirection 151

Conglomeration 159

Recursion 165

Revert Method 172

Extend Method 181

Delegated Conglomeration 187

Redirected Recursion 193

Trusted Delegation 200

Trusted Redirection 209

Deputized Delegation 216

Deputized Redirection 222

6 Intermediate Pattern Compositions 229

Fulfill Method 231

Retrieve New 235

xiii

Contents ix

Retrieve Shared 240

Objectifier 244

Object Recursion 251

7 Gang of Four Pattern Compositions 259

7.1 Creational Patterns 260

7.1.1 Abstract Factory 260

7.1.2 Factory Method 263

7.2 Structural Patterns 265

7.2.1 Decorator 265

7.2.2 Proxy 269

7.3 Behavioral Patterns 273

7.3.1 Chain of Responsibility 273

7.3.2 Template Method 275

7.4 Conclusion 279

A ρ-Calculus 281

A.1 Reliance Operators 282

A.2 Transitivity and Isotopes 285

A.3 Similarity 286

A.4 EDP Formalisms 287

A.5 Composition and Reduction Rules 291

A.6 Pattern Instance Notation and Roles 293

A.7 EDP Definitions 295

A.7.1 Create Object 295

A.7.2 Retrieve 296

A.7.3 Inheritance 298

A.7.4 Abstract Interface 298

A.7.5 Delegation 299

A.7.6 Redirection 300

A.7.7 Conglomeration 300

A.7.8 Recursion 301

A.7.9 Revert Method 301

A.7.10 Extend Method 302

A.7.11 Delegated Conglomeration 303

A.7.12 Redirected Recursion 303

A.7.13 Trusted Delegation 304

A.7.14 Trusted Redirection 305

A.7.15 Deputized Delegation 306

A.7.16 Deputized Redirection 307

xiv

x Contents

A.8 Intermediate Pattern Definitions 308

A.8.1 Fulfill Method 308

A.8.2 Retrieve New 309

A.8.3 Retrieve Shared 310

A.8.4 Objectifier 311

A.8.5 Object Recursion 312

A.9 Gang of Four Pattern Definitions 313

A.9.1 Abstract Factory 313

A.9.2 Factory Method 314

A.9.3 Decorator 316

A.9.4 Proxy 317

A.9.5 Chain of Responsibility 318

A.9.6 Template Method 319

Bibliography 321

Index 325

Figures

2.1 Decorator’s usual example UML 19

2.2 Objectifier as UML 20

2.3 Object Recursion as UML 20

2.4 A simple method call as UML 23

2.5 The parts of a method call 31

2.6 A simple design space 34

2.7 A simple design space with EDPs 35

2.8 Our first four EDPs 39

2.9 The design space extended to three dimensions 39

2.10 The design space with method similarity fixed to similar 40

2.11 Recursion Example UML 42

2.12 Deputized Redirection example UML 42

3.1 UML collaboration diagram 47

3.2 Strategy as pattern:role tags in UML 48

3.3 Huge UML of a not-so-huge system 48

3.4 Multiple instances of Strategy as pattern:role tags in UML 49

3.5 Collapsed PINbox 50

3.6 Collapsed PINbox as annotation 50

3.7 Singleton and Abstract Factory in class diagram 50

3.8 Template Method in sequence diagram 51

3.9 Standard PINbox 51

3.10 PIN used with UML class diagram 52

3.11 PIN used with UML sequence diagram 53

3.12 Standard PIN role connections 54

3.13 Blank expanded PIN instance 55

3.14 Expanded PIN instance 56

3.15 Expanded PIN instance using UML 57

3.16 A need for multiple related PINboxes 59

3.17 Stacked PINbox 60

3.18 Multiple Strategy instances as PINboxes 61

3.19 Showing the interaction between multiple Strategy PINboxes 62

3.20 Abstract Factory as part of a larger UML diagram 63

3.21 Abstract Factory subsumed within the expanded PINbox 64

3.22 Coalesced PINbox 65

4.1 Abstract Interface and Inheritance EDPs as UML 68

4.2 Internal definition of Fulfill Method as UML 69

4.3 Fulfill Method as simple connected PINboxes 69

4.4 Fulfill Method as expanded PINbox 69

4.5 Fulfill Method as standard PINbox 70

4.6 Flipping our EDPs in Fulfill Method—oops 71

4.7 Flipped EDPs as PINboxes 72

4.8 Alternative classes that can fulfill an Abstract Interface EDP 75

4.9 Alternative structures that can fulfill an Inheritance EDP 76

4.10 Decorator’s usual example UML 78

4.11 Fulfill Method definition as annotated UML 79

4.12 Objectifier UML annotated with PIN 80

4.13 Objectifier and Trusted Redirection 81

4.14 Object Recursion annotated with PIN 82

4.15 Object Recursion as just PIN 83

4.16 Object Recursion and Extend Method 84

4.17 Decorator annotated with PIN 85

4.18 Decorator as PIN 86

4.19 Decorator instance as a PINbox 86

4.20 Expanding Decorator: one level 87

4.21 Expanding Decorator: two levels 88

4.22 Expanding Decorator: three levels 89

4.23 Expanding Decorator: four levels 90

4.24 Delegation before Rename Method refactoring 93

4.25 Delegation after Rename Method refactoring—Redirection 94

4.26 Delegation before Move Method refactoring 95

4.27 The design space with method similarity fixed to dissimilar 96

4.28 Delegation after Move Method refactoring: boring case 97

4.29 Delegation after Move Method refactoring: into same type 97

4.30 Delegation after Move Method refactoring: Delegated Conglomeration 97

4.31 Delegation after Move Method refactoring: Conglomeration 98

4.32 Delegation after Move Method refactoring: Trusted Delegation 98

4.33 Delegation after Move Method refactoring: Revert Method 99

4.34 Delegation after Move Method refactoring: Deputized Delegation 99

4.35 Summarizing refactoring effects so far 100

4.36 Implicit used-by relationships among the EDPs and selected other

patterns 102

4.37 The full method-call EDP design space: dissimilar method 103

4.38 The full method-call EDP design space: similar method 104

4.39 Method-call EDP refactoring relations 106

5.1 Polymorphic approach 173

5.2 Subclassing approach 175

5.3 UI class cluster showing an instance of Trusted Delegation 203

5.4 UI class cluster showing an instance of Trusted Redirection . 211

5.5 UI class cluster showing an instance of Deputized Delegation . . 218

5.6 UI class cluster showing an instance of Deputized Redirection 225

7.1 Abstract Factory subsumed within the expanded PINbox 261

7.2 Reducing the diagram to just one instance of Abstract Factory . 262

7.3 Simplifying Figure 7.2 264

7.4 Abstract Factory as PIN only 265

7.5 Factory Method subsumed within the expanded PINbox 266

7.6 Factory Method as PIN only 267

7.7 Decorator subsumed with the expanded PINbox 268

7.8 Decorator as PIN only 269

7.9 Decorator expanded three levels deep and flattened 270

7.10 Proxy subsumed with the expanded PINbox 271

7.11 Proxy as PIN only 272

7.12 Proxy PIN reorganized to better match Decorator 272

7.13 Chain of Responsibility subsumed within the expanded PINbox 274

7.14 Chain of Responsibility as PIN only 275

7.15 Template Method subsumed within the expanded PINbox 276

7.16 Template Method reduced to a single instance . 277

7.17 Template Method as PIN only 278

7.18 Template Method PIN reorganized to better match Decorator 279

7.19 Factory Method redefined using Template Method 279

A.1 The full method call EDP design space: similar method 288

A.2 The full method call EDP design space: dissimilar method 289

A.3 Standard PINbox 294

A.4 Expanded PIN instance 294

Tables

2.1 Pattern pieces sorted into three categories of a pattern definition 22

2.2 All interactions between entities of object-oriented programming 28

2.3 Nonscoping interactions between entities of object-oriented

programming 28

A.1 All interactions between entities of object-oriented programming 283

A.2 Nonscoping interactions between entities of object-oriented

programming 284

Listings

2.1 A simple method call as pseudocode 24

2.2 Fields within classes, instances, and namespaces, as defined and used

in C++ 26

2.3 A Java class, and one possible equivalent object and type 27

2.4 Typing as context 29

2.5 A method call chain as pseudocode 30

2.6 Simple method call for Figure 2.5 31

2.7 Example of a Recursion method call in Java 36

2.8 Example of a Delegation method call in C++ 36

2.9 Example of a Redirection method call in Objective-C 37

2.10 Example of a Conglomeration method call in Java 38

5.1 Uninitialized data 118

5.2 Fixed default values 120

5.3 Dynamic initialization 121

5.4 Create Object Implementation 125

5.5 Retrieve with an update 126

5.6 Retrieve in a temporary variable 127

5.7 Basic inheritance example in Objective-C 131

5.8 Overriding an implementation 132

5.9 Implementation assumption mismatch 133

5.10 Obvious fix—but likely not feasible 134

5.11 Fixing a bug while leaving old code in place 134

5.12 Using Redirection to hide part of an interface 137

5.13 Animals almost all move but in very different ways 141

5.14 CEO delegates out responsibilities 145

5.15 Tom paints the fence with help 152

5.16 Prep work and cleanup are important 153

5.17 Prep work and cleanup are decomposable 160

5.18 Instance swapping for protocol fallback in C++ 173

5.19 Auto fallback/forward using Revert Method . 176

5.20 Using Redirection in Python to add behavior. 182

5.21 Using Extend Method to add behavior 182

5.22 Inviting friends naively in Java 187

5.23 A slightly better approach for inviting friends 188

5.24 Delegated Conglomeration in Java 188

5.25 Traditional iteration and invocation in C 193

5.26 Object-oriented iteration and invocation in C++ 193

5.27 Basic Redirected Recursion in C++ 194

5.28 Paratroopers implementing Redirected Recursion 195

5.29 UI widgets demonstrating Trusted Delegation in C++ 201

5.30 Event handler in C++ showing Trusted Redirection 210

5.31 UI widgets demonstrating Deputized Delegation in C++ 216

5.32 UI widgets demonstrating Deputized Redirection in C++ 222

6.1 Conditionals to select behavior 246

6.2 Using Objectifier to select behavior 247

A.1 Simple code example