Clean Code Cookbook: Recipes to Improve the Design and Quality of your Code

Cover
Copyright
Table of Contents
Foreword
Preface
	Who This Book Is For
	How This Book Is Organized
	What You Need to Use This Book
	Access This Book in Digital Format
	Conventions Used in This Book
	Using Code Examples
	O’Reilly Online Learning
	How to Contact Us
	Acknowledgments
Chapter 1. Clean Code
	1.1 What Is a Code Smell?
	1.2 What Is Refactoring?
	1.3 What Is a Recipe?
	1.4 Why Clean Code?
	1.5 Readability, Performance, or Both
	1.6 Software Types
	1.7 Machine-Generated Code
	1.8 Naming Considerations Throughout the Book
	1.9 Design Patterns
	1.10 Programming Language Paradigms
	1.11 Objects Versus Classes
	1.12 Changeability
Chapter 2. Setting Up the Axioms
	2.0 Introduction
	2.1 Why Is It a Model?
	2.2 Why Is It Abstract?
	2.3 Why Is It Programmable?
	2.4 Why Is It Partial?
	2.5 Why Is It Explanatory?
	2.6 Why Is It About Reality?
	2.7 Inferring the Rules
	2.8 The One and Only Software Design Principle
		The Problem
		Models to the Rescue
		The Importance of the Bijection
		Common Cases That Violate Bijection
		The Effect on Language When You Build Models
Chapter 3. Anemic Models
	3.0 Introduction
	3.1 Converting Anemic Objects to Rich Objects
		Problem
		Solution
		Discussion
		Related Recipes
	3.2 Identifying the Essence of Your Objects
		Problem
		Solution
		Discussion
		Related Recipes
	3.3 Removing Setters from Objects
		Problem
		Solution
		Discussion
		Related Recipes
	3.4 Removing Anemic Code Generators
		Problem
		Solution
		Discussion
		Related Recipes
	3.5 Removing Automatic Properties
		Problem
		Solution
		Discussion
		Related Recipes
	3.6 Removing DTOs
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	3.7 Completing Empty Constructors
		Problem
		Solution
		Discussion
		Related Recipes
	3.8 Removing Getters
		Problem
		Solution
		Discussion
		Related Recipes
	3.9 Preventing Object Orgy
		Problem
		Solution
		Discussion
		Related Recipes
	3.10 Removing Dynamic Properties
		Problem
		Solution
		Discussion
		Related Recipes
Chapter 4. Primitive Obsession
	4.0 Introduction
	4.1 Creating Small Objects
		Problem
		Solution
		Discussion
		Related Recipes
	4.2 Reifying Primitive Data
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	4.3 Reifying Associative Arrays
		Problem
		Solution
		Discussion
		Related Recipes
	4.4 Removing String Abuses
		Problem
		Solution
		Discussion
		Related Recipes
	4.5 Reifying Timestamps
		Problem
		Solution
		Discussion
		Related Recipes
	4.6 Reifying Subsets as Objects
		Problem
		Solutions
		Discussion
		Related Recipes
	4.7 Reifying String Validations
		Problem
		Solution
		Discussion
		Related Recipes
	4.8 Removing Unnecessary Properties
		Problem
		Solution
		Discussion
		Related Recipes
	4.9 Creating Date Intervals
		Problem
		Solution
		Discussion
		Related Recipes
Chapter 5. Mutability
	5.0 Introduction
		A Different Approach to Mutability
	5.1 Changing var to const
		Problem
		Solution
		Discussion
		Related Recipes
	5.2 Declaring Variables to Be Variable
		Problem
		Solution
		Discussion
		Related Recipes
	5.3 Forbidding Changes in the Essence
		Problem
		Solution
		Discussion
		Related Recipes
	5.4 Avoiding Mutable const Arrays
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	5.5 Removing Lazy Initialization
		Problem
		Solution
		Discussion
		Related Recipes
	5.6 Freezing Mutable Constants
		Problem
		Solution
		Discussion
		Related Recipes
	5.7 Removing Side Effects
		Problem
		Solution
		Discussion
		Related Recipes
	5.8 Preventing Hoisting
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
Chapter 6. Declarative Code
	6.0 Introduction
	6.1 Narrowing Reused Variables
		Problem
		Solution
		Discussion
		Related Recipes
	6.2 Removing Empty Lines
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	6.3 Removing Versioned Methods
		Problem
		Solution
		Discussion
		Related Recipes
	6.4 Removing Double Negatives
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	6.5 Changing Misplaced Responsibilities
		Problem
		Solution
		Discussion
		Related Recipes
	6.6 Replacing Explicit Iterations
		Problem
		Solution
		Discussion
		Related Recipes
	6.7 Documenting Design Decisions
		Problem
		Solution
		Discussion
		Related Recipes
	6.8 Replacing Magic Numbers with Constants
		Problem
		Solution
		Discussion
		Related Recipes
	6.9 Separating “What” and “How”
		Problem
		Solution
		Discussion
		Related Recipes
	6.10 Documenting Regular Expressions
		Problem
		Solution
		Discussion
		Related Recipes
	6.11 Rewriting Yoda Conditions
		Problem
		Solution
		Discussion
		Related Recipes
	6.12 Removing Comedian Methods
		Problem
		Solution
		Discussion
		Related Recipes
	6.13 Avoiding Callback Hell
		Problem
		Solution
		Discussion
		Related Recipes
	6.14 Generating Good Error Messages
		Problem
		Solution
		Discussion
		Related Recipes
	6.15 Avoiding Magic Corrections
		Problem
		Solution
		Discussion
		Related Recipes
Chapter 7. Naming
	7.0 Introduction
	7.1 Expanding Abbreviations
		Problem
		Solution
		Discussion
		Related Recipes
	7.2 Renaming and Breaking Helpers and Utils
		Problem
		Solution
		Discussion
		Related Recipes
	7.3 Renaming MyObjects
		Problem
		Solution
		Discussion
	7.4 Renaming Result Variables
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	7.5 Renaming Variables Named After Types
		Problem
		Solution
		Discussion
		Related Recipes
	7.6 Renaming Long Names
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	7.7 Renaming Abstract Names
		Problem
		Solution
		Discussion
		Related Recipes
	7.8 Correcting Spelling Mistakes
		Problem
		Solution
		Discussion
		Related Recipes
	7.9 Removing Class Names from Attributes
		Problem
		Solution
		Discussion
		Related Recipes
	7.10 Removing the First Letter from Classes and Interfaces
		Problem
		Solution
		Discussion
		Related Recipes
	7.11 Renaming Basic / Do Functions
		Problem
		Solution
		Discussion
	7.12 Converting Plural Classes to Singular
		Problem
		Solution
		Discussion
	7.13 Removing “Collection” from Names
		Problem
		Solution
		Discussion
		Related Recipes
	7.14 Removing “Impl” Prefix/Suffix from Class Names
		Problem
		Solution
		Discussion
		Related Recipes
	7.15 Renaming Arguments According to Role
		Problem
		Solution
		Discussion
		Related Recipes
	7.16 Removing Redundant Parameter Names
		Problem
		Solution
		Discussion
		Related Recipes
	7.17 Removing Gratuitous Context from Names
		Problem
		Solution
		Discussion
		Related Recipes
	7.18 Avoiding Data Naming
		Problem
		Solution
		Discussion
		Related Recipes
Chapter 8. Comments
	8.0 Introduction
	8.1 Removing Commented Code
		Problem
		Solution
		Discussion
		Related Recipes
	8.2 Removing Obsolete Comments
		Problem
		Solution
		Discussion
		Related Recipes
	8.3 Removing Logical Comments
		Problem
		Solution
		Discussion
		Related Recipes
	8.4 Removing Getter Comments
		Problem
		Solution
		Discussion
		Related Recipes
	8.5 Converting Comments to Function Names
		Problem
		Solution
		Discussion
		Related Recipes
	8.6 Removing Comments Inside Methods
		Problem
		Solution
		Discussion
		Related Recipes
	8.7 Replacing Comments with Tests
		Problem
		Solution
		Discussion
		Related Recipes
Chapter 9. Standards
	9.0 Introduction
	9.1 Following Code Standards
		Problem
		Solution
		Discussion
		Related Recipes
	9.2 Standardizing Indentations
		Problem
		Solution
		Discussion
		Related Recipes
	9.3 Unifying Case Conventions
		Problem
		Solution
		Discussion
		Related Recipes
	9.4 Writing Code in English
		Problem
		Solution
		Discussion
	9.5 Unifying Parameter Order
		Problem
		Solution
		Discussion
		Related Recipes
	9.6 Fixing Broken Windows
		Problem
		Solution
		Discussion
		Related Recipes
Chapter 10. Complexity
	10.0 Introduction
	10.1 Removing Repeated Code
		Problem
		Solution
		Discussion
		Related Recipes
	10.2 Removing Settings/Configs and Feature Toggles
		Problem
		Solution
		Discussion
		Related Recipes
	10.3 Changing State as Properties
		Problem
		Solution
		Discussion
		Related Recipes
	10.4 Removing Cleverness from Code
		Problem
		Solution
		Discussion
		Related Recipes
	10.5 Breaking Multiple Promises
		Problem
		Solution
		Discussion
	10.6 Breaking Long Chains of Collaborations
		Problem
		Solution
		Discussion
		Related Recipes
	10.7 Extracting a Method to an Object
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	10.8 Looking After Array Constructors
		Problem
		Solution
		Discussion
		Related Recipes
	10.9 Removing Poltergeist Objects
		Problem
		Solution
		Discussion
		Related Recipes
Chapter 11. Bloaters
	11.0 Introduction
	11.1 Breaking Too Long Methods
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	11.2 Reducing Excess Arguments
		Problem
		Solution
		Discussion
		Related Recipes
	11.3 Reducing Excess Variables
		Problem
		Solution
		Discussion
		Related Recipes
	11.4 Removing Excessive Parentheses
		Problem
		Solution
		Discussion
		Related Recipes
	11.5 Removing Excess Methods
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	11.6 Breaking Too Many Attributes
		Problem
		Solution
		Discussion
		Related Recipes
	11.7 Reducing Import Lists 
		Problem
		Solution
		Discussion
		Related Recipes
	11.8 Breaking “And” Functions
		Problem
		Solution
		Discussion
		Related Recipes
	11.9 Breaking Fat Interfaces
		Problem
		Solution
		Discussion
		Related Recipes
Chapter 12. YAGNI
	12.0 Introduction
	12.1 Removing Dead Code
		Problem
		Solution
		Discussion
		Related Recipes
	12.2 Using Code Instead of Diagrams
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	12.3 Refactoring Classes with One Subclass
		Problem
		Solution
		Discussion
		Related Recipes
	12.4 Removing One-Use Interfaces
		Problem
		Solution
		Discussion
		Related Recipes
	12.5 Removing Design Pattern Abuses
		Problem
		Solution
		Discussion
		Related Recipes
	12.6 Replacing Business Collections
		Problem
		Solution
		Discussion
		Related Recipes
Chapter 13. Fail Fast
	13.0 Introduction
	13.1 Refactoring Reassignment of Variables
		Problem
		Solution
		Discussion
		Related Recipes
	13.2 Enforcing Preconditions
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	13.3 Using Stricter Parameters
		Problem
		Solution
		Discussion
		Related Recipes
	13.4 Removing Default from Switches
		Problem
		Solution
		Discussion
		Related Recipes
	13.5 Avoiding Modifying Collections While Traversing
		Problem
		Solution
		Discussion
		Related Recipes
	13.6 Redefining Hash and Equality
		Problem
		Solution
		Discussion
		Related Recipes
	13.7 Refactoring Without Functional Changes
		Problem
		Solution
		Discussion
Chapter 14. Ifs
	14.0 Introduction
	14.1 Replacing Accidental Ifs with Polymorphism
		Problem
		Solution
		Discussion
	14.2 Renaming Flag Variables for Events
		Problem
		Solution
		Discussion
		Related Recipes
	14.3 Reifying Boolean Variables
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	14.4 Replacing Switch/Case/Elseif Statements
		Problem
		Solution
		Discussion
		Related Recipes
	14.5 Replacing Hardcoded If Conditions with Collections
		Problem
		Solution
		Discussion
		Related Recipes
	14.6 Changing Boolean to Short-Circuit Conditions
		Problem
		Solution
		Discussion
		Related Recipes
	14.7 Adding Implicit Else
		Problem
		Solution
		Discussion
		Related Recipes
	14.8 Rewriting Conditional Arrow Code
		Problem
		Solution
		Discussion
		Related Recipes
	14.9 Avoiding Short-Circuit Hacks
		Problem
		Solution
		Discussion
		Related Recipes
	14.10 Rewriting Nested Arrow Code
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	14.11 Preventing Return Boolean Values for Condition Checks
		Problem
		Solution
		Discussion
		Related Recipes
	14.12 Changing Comparison Against Booleans
		Problem
		Solution
		Discussion
		Related Recipes
	14.13 Extracting from Long Ternaries
		Problem
		Solution
		Discussion
		Related Recipes
	14.14 Converting Nonpolymorphic Functions to Polymorphic
		Problem
		Solution
		Discussion
		Related Recipes
	14.15 Changing Equal Comparison
		Problem
		Solution
		Discussion
		Related Recipes
	14.16 Reifying Hardcoded Business Conditions
		Problem
		Solution
		Discussion
		Related Recipes
	14.17 Removing Gratuitous Booleans
		Problem
		Solution
		Discussion
		Related Recipes
	14.18 Rewriting Nested Ternaries
		Problem
		Solution
		Discussion
		Related Recipes
Chapter 15. Null
	15.0 Introduction
	15.1 Creating Null Objects
		Problem
		Solution
		Discussion
		See Also
	15.2 Removing Optional Chaining
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	15.3 Converting Optional Attributes to a Collection
		Problem
		Solution
		Discussion
		Related Recipes
	15.4 Using Real Objects for Null
		Problem
		Solution
		Discussion
		Related Recipes
	15.5 Representing Unknown Locations Without Using Null
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
Chapter 16. Premature Optimization
	16.0 Introduction
	16.1 Avoiding IDs on Objects
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	16.2 Removing Premature Optimization
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	16.3 Removing Bitwise Premature Optimizations
		Problem
		Solution
		Discussion
		Related Recipes
	16.4 Reducing Overgeneralization
		Problem
		Solution
		Discussion
		Related Recipes
	16.5 Changing Structural Optimizations
		Problem
		Solution
		Discussion
		Related Recipes
	16.6 Removing Anchor Boats
		Problem
		Solution
		Discussion
		Related Recipes
	16.7 Extracting Caches from Domain Objects
		Problem
		Solution
		Discussion
		Related Recipes
	16.8 Removing Callback Events Based on Implementation
		Problem
		Solution
		Discussion
		Related Recipes
	16.9 Removing Queries from Constructors
		Problem
		Solution
		Discussion
		Related Recipes
	16.10 Removing Code from Destructors
		Problem
		Solution
		Discussion
		Related Recipes
Chapter 17. Coupling
	17.0 Introduction
	17.1 Making Hidden Assumptions Explicit
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	17.2 Replacing Singletons
		Problem
		Solution
		Discussion
		Related Recipes
	17.3 Breaking God Objects
		Problem
		Solution
		Discussion
		Related Recipes
	17.4 Breaking Divergent Change
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	17.5 Converting 9999 Special Flag Values to Normal
		Problem
		Solution
		Discussion
		Related Recipes
	17.6 Removing Shotgun Surgery
		Problem
		Solution
		Discussion
	17.7 Removing Optional Arguments
		Problem
		Solution
		Discussion
		Related Recipes
	17.8 Preventing Feature Envy
		Problem
		Solution
		Discussion
		Related Recipes
	17.9 Removing the Middleman
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	17.10 Moving Default Arguments to the End
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	17.11 Avoiding the Ripple Effect
		Problem
		Solution
		Discussion
		Related Recipes
	17.12 Removing Accidental Methods on Business Objects
		Problem
		Solution
		Discussion
	17.13 Removing Business Code from the User Interface
		Problem
		Solution
		Discussion
		Related Recipes
	17.14 Changing Coupling to Classes
		Problem
		Solution
		Discussion
		Related Recipes
	17.15 Refactoring Data Clumps
		Problem
		Solution
		Discussion
		Related Recipes
	17.16 Breaking Inappropriate Intimacy
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	17.17 Converting Fungible Objects
		Problem
		Solution
		Discussion
		Related Recipes
Chapter 18. Globals
	18.0 Introduction
	18.1 Reifying Global Functions
		Problem
		Solution
		Discussion
		Related Recipes
	18.2 Reifying Static Functions
		Problem
		Solution
		Discussion
		Related Recipes
	18.3 Replacing GoTo with Structured Code
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	18.4 Removing Global Classes
		Problem
		Solutions
		Discussion
		Related Recipes
	18.5 Changing Global Date Creation
		Problem
		Solution
		Discussion
		Related Recipes
Chapter 19. Hierarchies
	19.0 Introduction
	19.1 Breaking Deep Inheritance
		Problem
		Solution
		Discussion
		Related Recipes
	19.2 Breaking Yo-Yo Hierarchies
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	19.3 Breaking Subclassification for Code Reuse
		Problem
		Solution
		Discussion
		Related Recipes
	19.4 Replacing “is-a” Relationship with Behavior
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	19.5 Removing Nested Classes
		Problem
		Solution
		Discussion
		See Also
	19.6 Renaming Isolated Classes
		Problem
		Solution
		Discussion
		Related Recipes
	19.7 Making Concrete Classes Final
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	19.8 Defining Class Inheritance Explicitly
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	19.9 Migrating Empty Classes
		Problem
		Solution
		Discussion
		Related Recipes
	19.10 Delaying Premature Classification
		Problem
		Solution
		Discussion
		Related Recipes
	19.11 Removing Protected Attributes
		Problem
		Solution
		Discussion
		Related Recipes
	19.12 Completing Empty Implementations
		Problem
		Solution
		Discussion
		Related Recipes
Chapter 20. Testing
	20.0 Introduction
	20.1 Testing Private Methods
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	20.2 Adding Descriptions to Assertions
		Problem
		Solution
		Discussion
		See Also
	20.3 Migrating assertTrue to Specific Assertions
		Problem
		Solution
		Discussion
		Related Recipes
	20.4 Replacing Mocks with Real Objects
		Problem
		Solution
		Discussion
		Related Recipes
	20.5 Refining Generic Assertions
		Problem
		Solution
		Discussion
		Related Recipes
	20.6 Removing Flaky Tests
		Problem
		Solution
		Discussion
		Related Recipes
	20.7 Changing Float Number Assertions
		Problem
		Solution
		Discussion
		Related Recipes
	20.8 Changing Test Data to Realistic Data
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	20.9 Protecting Tests Violating Encapsulation
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	20.10 Removing Irrelevant Test Information
		Problem
		Solution
		Discussion
		Related Recipes
	20.11 Adding Coverage for Every Merge Request
		Problem
		Solution
		Discussion
		Related Recipes
	20.12 Rewriting Tests Depending on Dates
		Problem
		Solution
		Discussion
		Related Recipes
	20.13 Learning a New Programming Language
		Problem
		Solution
		Discussion
		See Also
Chapter 21. Technical Debt
	21.0 Introduction
	21.1 Removing Production-Dependent Code
		Problem
		Solution
		Discussion
		Related Recipes
	21.2 Removing Defect Trackers
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	21.3 Removing Warning/Strict Off
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	21.4 Preventing and Removing ToDos and FixMes
		Problem
		Solution
		Discussion
		Related Recipes
Chapter 22. Exceptions
	22.0 Introduction
	22.1 Removing Empty Exception Blocks
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	22.2 Removing Unnecessary Exceptions
		Problem
		Solution
		Discussion
		Related Recipes
	22.3 Rewriting Exceptions for Expected Cases
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	22.4 Rewriting Nested Try/Catches
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	22.5 Replacing Return Codes with Exceptions
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	22.6 Rewriting Exception Arrow Code
		Problem
		Solution
		Discussion
		Related Recipes
	22.7 Hiding Low-Level Errors from End Users
		Problem
		Solution
		Discussion
		Related Recipes
	22.8 Narrowing Exception Tries
		Problem
		Solution
		Discussion
		Related Recipes
Chapter 23. Metaprogramming
	23.0 Introduction
	23.1 Removing Metaprogramming Usage
		Problem
		Solution
		Discussion
	23.2 Reifying Anonymous Functions
		Problem
		Solution
		Discussion
		Related Recipes
	23.3 Removing Preprocessors
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	23.4 Removing Dynamic Methods
		Problem
		Solution
		Discussion
		Related Recipes
Chapter 24. Types
	24.0 Introduction
	24.1 Removing Type Checking
		Problem
		Solution
		Discussion
		Related Recipes
	24.2 Dealing with Truthy Values
		Problem
		Solution
		Discussion
		Related Recipes
	24.3 Changing Float Numbers to Decimals
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
Chapter 25. Security
	25.0 Introduction
	25.1 Sanitizing Inputs
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	25.2 Changing Sequential IDs
		Problem
		Solution
		Discussion
		See Also
		Related Recipes
	25.3 Removing Package Dependencies
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	25.4 Replacing Evil Regular Expressions
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
	25.5 Protecting Object Deserialization
		Problem
		Solution
		Discussion
		Related Recipes
		See Also
Glossary of Terms
Index
About the Author
Colophon