The Object-Oriented Thought Process

83 Private Implementation Methods 83 Conclusion 84 References 84 Example Code Used in This Chapter 84 5 Class Design Guidelines 87 Modeling Real World Systems 87 Identifying the Public Interfaces 88 The Minimum Public Interface 88 Hiding the Implementation 89 Designing Robust Constructors (and Perhaps Destructors) 89 Designing Error Handling into a Class 90 Documenting a Class and Using Comments 91 Building Objects with the Intent to Cooperate 91 Designing with Reuse in Mind 91 Documenting a Class and Using Comments 91 Designing with Extensibility in Mind 92 Making Names Descriptive 92 Abstracting Out Nonportable Code 93 Providing a Way to Copy and Compare Objects 93 Keeping the Scope as Small as Possible 94 A Class Should Be Responsible for Itself 95 Designing with Maintainability in Mind 96 Using Iteration 97 Testing the Interface 97 Using Object Persistence 99 Serializing and Marshaling Objects 100 Conclusion 100 References 101 Example Code Used in This Chapter 101 6 Designing with Objects 103 Design Guidelines 103 Performing the Proper Analysis 107 Developing a Statement of Work 107 Gathering the Requirements 107 Developing a Prototype of the User Interface 108 Identifying the Classes 108 Determining the Responsibilities of Each Class 108 Determining How the Classes Collaborate with Each Other 109 Creating a Class Model to Describe the System 109 Case Study: A Blackjack Example 109 Using CRC Cards 111 Identifying the Blackjack Classes 112 Identifying the Classes' Responsibilities 115 UML Use-Cases: Identifying the Collaborations 120 First Pass at CRC Cards 124 UML Class Diagrams: The Object Model 126 Prototyping the User Interface 127 Conclusion 127 References 128 7 Mastering Inheritance and Composition 129 Reusing Objects 129 Inheritance 130 Generalization and Specialization 133 Design Decisions 134 Composition 135 Representing Composition with UML 136 Why Encapsulation Is Fundamental to OO 138 How Inheritance Weakens Encapsulation 139 A Detailed Example of Polymorphism 141 Object Responsibility 141 Conclusion 145 References 146 Example Code Used in This Chapter 146 8 Frameworks and Reuse: Designing with Interfaces and Abstract Classes 151 Code: To Reuse or Not to Reuse? 151 What Is a Framework? 152 What Is a Contract? 153 Abstract Classes 154 Interfaces 157 Tying It All Together 159 The Compiler Proof 161 Making a Contract 162 System Plug-in-Points 165 An E-Business Example 165 An E-Business Problem 165 The Non-Reuse Approach 166 An E-Business Solution 168 The UML Object Model 168 Conclusion 173 References 173 Example Code Used in This Chapter 173 9 Building Objects 179 Composition Relationships 179 Building in Phases 181 Types of Composition 183 Aggregations 183 Associations 184 Using Associations and Aggregations Together 185 Avoiding Dependencies 186 Cardinality 186 Multiple Object Associations 189 Optional Associations 190 Tying It All Together: An Example 191 Conclusion 192 References 192 10 Creating Object Models with UML 193 What Is UML? 193 The Structure of a Class Diagram 194 Attributes and Methods 196 Attributes 196 Methods 197 Access Designations 197 Inheritance 198 Interfaces 200 Composition 201 Aggregations 201 Associations 201 Cardinality 204 Conclusion 205 References 205 11 Objects and Portable Data: XML 207 Portable Data 207 The Extensible Markup Language (XML) 209 XML Versus HTML 209 XML and Object-Oriented Languages 210 Sharing Data Between Two Companies 211 Validating the Document with the Document Type Definition (DTD) 212 Integrating the DTD into the XML Document 213 Using Cascading Style Sheets 220 Conclusion 223 References 223 12 Persistent Objects: Serialization and Relational Databases 225 Persistent Objects Basics 225 Saving the Object to a Flat File 227 Serializing a File 227 Implementation and Interface Revisited 229 What About the Methods? 231 Using XML in the Serialization Process 231 Writing to a Relational Database 234 Accessing a Relational Database 236 Loading the Driver 238 Making the Connection 238 The SQL Statements 239 Conclusion 242 References 242 Example Code Used in This Chapter 242 13 Objects and the Internet 247 Evolution of Distributed Computing 247 Object-Based Scripting Languages 248 A JavaScript Validation Example 250 Objects in a Web Page 253 JavaScript Objects 254 Web Page Controls 255 Sound Players 257 Movie Players 257 Flash 258 Distributed Objects and the Enterprise 258 The Common Object Request Broker Architecture (CORBA) 259 Web Services Definition 263 Web Services Code 267 Invoice.cs 267 Invoice.vb 268 Conclusion 270 References 270 14 Objects and Client/Server Applications 271 Client/Server Approaches 271 Proprietary Approach 272 Serialized Object Code 272 Client Code 273 Server Code 275 Running the Proprietary Client/Server Example 276 Nonproprietary Approach 278 Object Definition Code 278 Client Code 280 Server Code 281 Running the Nonproprietary Client/Server Example 283 Conclusion 283 References 284 Example Code Used in This Chapter 284 15 Design Patterns 287 Why Design Patterns? 288 Smalltalk's Model/View/Controller 289 Types of Design Patterns 290 Creational Patterns 291 Structural Patterns 295 Behavioral Patterns 298 Antipatterns 299 Conclusion 300 References 300 Example Code Used in This Chapter 301 Index 309