Practical Object-Oriented Design in Ruby An Agile Primer

Introduction         xvii

Acknowledgments         xxi

About the Author         xxiii

Chapter 1: Object-Oriented Design         1

In Praise of Design   2

The Tools of Design   4

The Act of Design   7

A Brief Introduction to Object-Oriented Programming   11

Summary 14

Chapter 2: Designing Classes with a Single Responsibility         15

Deciding What Belongs in a Class   16

Grouping Methods into Classes   16

Organizing Code to Allow for Easy Changes   16

Creating Classes That Have a Single Responsibility   17

Writing Code That Embraces Change   24

Finally, the Real Wheel   33

Summary   34

Chapter 3: Managing Dependencies         35

Understanding Dependencies   36

Writing Loosely Coupled Code   39

Managing Dependency Direction   51

Summary   57

Chapter 4: Creating Flexible Interfaces         59

Understanding Interfaces   59

Defining Interfaces   61

Public Interfaces   62

Private Interfaces   62

Responsibilities, Dependencies, and Interfaces   62

Finding the Public Interface   63

Writing Code That Puts Its Best (Inter)Face Forward   76

The Law of Demeter   80

Summary   83

Chapter 5: Reducing Costs with Duck Typing         85

Understanding Duck Typing   85

Writing Code That Relies on Ducks   95

Conquering a Fear of Duck Typing   100

Summary   104

Chapter 6: Acquiring Behavior Through Inheritance         105

Understanding Classical Inheritance   105

Recognizing Where to Use Inheritance   106

Misapplying Inheritance   114

Finding the Abstraction   116

Managing Coupling Between Superclasses and Subclasses   129

Summary 139

Chapter 7: Sharing Role Behavior with Modules         141

Understanding Roles   142

Writing Inheritable Code   158

Summary   162

Chapter 8: Combining Objects with Composition         163

Composing a Bicycle of Parts   164

Composing the Parts Object   168

Manufacturing Parts   176

The Composed Bicycle   180

Deciding Between Inheritance and Composition   184

Summary   190

Chapter 9: Designing Cost-Effective Tests         191

Intentional Testing   192

Testing Incoming Messages   200

Testing Private Methods   213

Testing Outgoing Messages   215

Testing Duck Types   219

Testing Inherited Code   229

Summary 240

Afterword         241

Index          243

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