Foreword to the First Edition xi Preface xiii Chapter 1: Refactoring: A First Example 1 The Starting Point 1 Comments on the Starting Program 3 The First Step in Refactoring 5 Decomposing the statement Function 6 Status: Lots of Nested Functions 22 Splitting the Phases of Calculation and Formatting 24 Status: Separated into Two Files (and Phases) 31 Reorganizing the Calculations by Type 34 Status: Creating the Data with the Polymorphic Calculator 41 Final Thoughts 43 Chapter 2: Principles in Refactoring 45 Defining Refactoring 45 The Two Hats 46 Why Should We Refactor? 47 When Should We Refactor? 50 Problems with Refactoring 55 Refactoring, Architecture, and Yagni 62 Refactoring and the Wider Software Development Process 63 Refactoring and Performance 64 Where Did Refactoring Come From? 67 Automated Refactorings 68 Going Further 70 Chapter 3: Bad Smells in Code 71 Mysterious Name 72 Duplicated Code 72 Long Function 73 Long Parameter List 74 Global Data 74 Mutable Data 75 Divergent Change 76 Shotgun Surgery 76 Feature Envy 77 Data Clumps 78 Primitive Obsession 78 Repeated Switches 79 Loops 79 Lazy Element 80 Speculative Generality 80 Temporary Field 80 Message Chains 81 Middle Man 81 Insider Trading 82 Large Class 82 Alternative Classes with Different Interfaces 83 Data Class 83 Refused Bequest 83 Comments 84 Chapter 4: Building Tests 85 The Value of Self-Testing Code 85 Sample Code to Test 87 A First Test 90 Add Another Test 93 Modifying the Fixture 95 Probing the Boundaries 96 Much More Than This 99 Chapter 5: Introducing the Catalog 101 Format of the Refactorings 101 The Choice of Refactorings 102 Chapter 6: A First Set of Refactorings 105 Extract Function 106 Inline Function 115 Extract Variable 119 Inline Variable 123 Change Function Declaration 124 Encapsulate Variable 132 Rename Variable 137 Introduce Parameter Object 140 Combine Functions into Class 144 Combine Functions into Transform 149 Split Phase 154 Chapter 7: Encapsulation 161 Encapsulate Record 162 Encapsulate Collection 170 Replace Primitive with Object 174 Replace Temp with Query 178 Extract Class 182 Inline Class 186 Hide Delegate 189 Remove Middle Man 192 Substitute Algorithm 195 Chapter 8: Moving Features 197 Move Function 198 Move Field 207 Move Statements into Function 213 Move Statements to Callers 217 Replace Inline Code with Function Call 222 Slide Statements 223 Split Loop 227 Replace Loop with Pipeline 231 Remove Dead Code 237 Chapter 9: Organizing Data 239 Split Variable 240 Rename Field 244 Replace Derived Variable with Query 248 Change Reference to Value 252 Change Value to Reference 256 Chapter 10: Simplifying Conditional Logic 259 Decompose Conditional 260 Consolidate Conditional Expression 263 Replace Nested Conditional with Guard Clauses 266 Replace Conditional with Polymorphism 272 Introduce Special Case 289 Introduce Assertion 302 Chapter 11: Refactoring APIs 305 Separate Query from Modifier 306 Parameterize Function 310 Remove Flag Argument 314 Preserve Whole Object 319 Replace Parameter with Query 324 Replace Query with Parameter 327 Remove Setting Method 331 Replace Constructor with Factory Function 334 Replace Function with Command 337 Replace Command with Function 344 Chapter 12: Dealing with Inheritance 349 Pull Up Method 350 Pull Up Field 353 Pull Up Constructor Body 355 Push Down Method 359 Push Down Field 361 Replace Type Code with Subclasses 362 Remove Subclass 369 Extract Superclass 375 Collapse Hierarchy 380 Replace Subclass with Delegate 381 Replace Superclass with Delegate 399 Bibliography 405 Index 409