Clean Code A Handbook of Agile Software Craftsmanship

by Martin, Robert C.

• ISBN13: 9780132350884
• ISBN10: 0132350882
• Edition: 1st
• Format: Paperback
• Copyright: 2008-08-01
• Publisher: Pearson

Summary

Even bad code can function. But if code isnrs"t clean, it can bring a development organization to its knees. Every year, countless hours and significant resources are lost because of poorly written code. But it doesnrs"t have to be that way. Noted software expert Robert C. Martin presents a revolutionary paradigm withClean Code: A Handbook of Agile Software Craftsmanship. Martin has teamed up with his colleagues from Object Mentor to distill their best agile practice of cleaning code "on the fly" into a book that will instill within you the values of a software craftsman and make you a better programmer-but only if you work at it. What kind of work will you be doing? Yours"ll be reading code-lots of code. And you will be challenged to think about whatrs"s right about that code, and whatrs"s wrong with it. More importantly, you will be challenged to reassess your professional values and your commitment to your craft. Clean Codeis divided into three parts. The first describes the principles, patterns, and practices of writing clean code. The second part consists of several case studies of increasing complexity. Each case study is an exercise in cleaning up code-of transforming a code base that has some problems into one that is sound and efficient. The third part is the payoff: a single chapter containing a list of heuristics and "smells" gathered while creating the case studies. The result is a knowledge base that describes the way we think when we write, read, and clean code. Readers will come away from this book understanding How to tell the difference between good and bad code How to write good code and how to transform bad code into good code How to create good names, good functions, good objects, and good classes How to format code for maximum readability How to implement complete error handling without obscuring code logic How to unit test and practice test-driven development This book is a must for any developer, software engineer, project manager, team lead, or systems analyst with an interest in producing better code.

Author Biography

Robert C. “Uncle Bob” Martin has been a software professional since 1970 and an international software consultant since 1990. He is founder and president of Object Mentor, Inc., a team of experienced consultants who mentor their clients worldwide in the fields of C++, Java, C#, Ruby, OO, Design Patterns, UML, Agile Methodologies, and eXtreme programming.

Table of Contents

Foreword	p. xix
Introduction	p. xxv
On the Cover	p. xxix
Clean Code	p. 1
There Will Be Code	p. 2
Bad Code	p. 3
The Total Cost of Owning a Mess	p. 4
Schools of Thought	p. 12
We Are Authors	p. 13
The Boy Scout Rule	p. 14
Prequel and Principles	p. 15
Conclusion	p. 15
Bibliography	p. 15
Meaningful Names	p. 17
Introduction	p. 17
Use Intention-Revealing Names	p. 18
Avoid Disinformation	p. 19
Make Meaningful Distinctions	p. 20
Use Pronounceable Names	p. 21
Use Searchable Names	p. 22
Avoid Encodings	p. 23
Avoid Mental Mapping	p. 25
Class Names	p. 25
Method Names	p. 25
Don't Be Cute	p. 26
Pick One Word per Concept	p. 26
Don't Pun	p. 26
Use Solution Domain Names	p. 27
Use Problem Domain Names	p. 27
Add Meaningful Context	p. 27
Don't Add Gratuitous Context	p. 29
Final Words	p. 30
Functions	p. 31
Small!	p. 34
Do One Thing	p. 35
One Level of Abstraction per Function	p. 36
Switch Statements	p. 37
Use Descriptive Names	p. 39
Function Arguments	p. 40
Have No Side Effects	p. 44
Command Query Separation	p. 45
Prefer Exceptions to Returning Error Codes	p. 46
Don't Repeat Yourself	p. 48
Structured Programming	p. 48
How Do You Write Functions Like This?	p. 49
Conclusion	p. 49
SetupTeardownIncluder	p. 50
Bibliography	p. 52
Comments	p. 53
Comments Do Not Make Up for Bad Code	p. 55
Explain Yourself in Code	p. 55
Good Comments	p. 55
Bad Comments	p. 59
Bibliography	p. 74
Formatting	p. 75
The Purpose of Formatting	p. 76
Vertical Formatting	p. 76
Horizontal Formatting	p. 85
Team Rules	p. 90
Uncle Bob's Formatting Rules	p. 90
Objects and Data Structures	p. 93
Data Abstraction	p. 93
Data/Object Anti-Symmetry	p. 95
The Law of Demeter	p. 97
Data Transfer Objects	p. 100
Conclusion	p. 101
Bibliography	p. 101
Error Handling	p. 103
Use Exceptions Rather Than Return Codes	p. 104
Write Your Try-Catch-Finally Statement First	p. 105
Use Unchecked Exceptions	p. 106
Provide Context with Exceptions	p. 107
Define Exception Classes in Terms of a Caller's Needs	p. 107
Define the Normal Flow	p. 109
Don't Return Null	p. 110
Don't Pass Null	p. 111
Conclusion	p. 112
Bibliography	p. 112
Boundaries	p. 113
Using Third-Party Code	p. 114
Exploring and Learning Boundaries	p. 116
Learning log4j	p. 116
Learning Tests Are Better Than Free	p. 118
Using Code That Does Not Yet Exist	p. 118
Clean Boundaries	p. 120
Bibliography	p. 120
Unit Tests	p. 121
The Three Laws of TDD	p. 122
Keeping Tests Clean	p. 123
Clean Tests	p. 124
One Assert per Test	p. 130
F.I.R.S.T	p. 132
Conclusion	p. 133
Bibliography	p. 133
Classes	p. 135
Class Organization	p. 136
Classes Should Be Small!	p. 136
Organizing for Change	p. 147
Bibliography	p. 151
Systems	p. 153
How Would You Build a City?	p. 154
Separate Constructing a System from Using It	p. 154
Scaling Up	p. 157
Java Proxies	p. 161
Pure Java AOP Frameworks	p. 163
AspectJ Aspects	p. 166
Test Drive the System Architecture	p. 166
Optimize Decision Making	p. 167
Use Standards Wisely, When They Add Demonstrable Value	p. 168
Systems Need Domain-Specific Languages	p. 168
Conclusion	p. 169
Bibliography	p. 169
Emergence	p. 171
Getting Clean via Emergent Design	p. 171
Simple Design Rule 1: Runs All the Tests	p. 172
Simple Design Rules 2-4: Refactoring	p. 172
No Duplication	p. 173
Expressive	p. 175
Minimal Classes and Methods	p. 176
Conclusion	p. 176
Bibliography	p. 176
Concurrency	p. 177
Why Concurrency?	p. 178
Challenges	p. 180
Concurrency Defense Principles	p. 180
Know Your Library	p. 182
Know Your Execution Models	p. 183
Beware Dependencies Between Synchronized Methods	p. 185
Keep Synchronized Sections Small	p. 185
Writing Correct Shut-Down Code Is Hard	p. 186
Testing Threaded Code	p. 186
Conclusion	p. 190
Bibliography	p. 191
Successive Refinement	p. 193
Table of Contents provided by Publisher. All Rights Reserved.

Excerpts

Which door represents your code? Which door represents your team or your company? Why are we in that room? Is this just a normal code review or have we found a stream of horrible problems shortly after going live? Are we debugging in a panic, poring over code that we thought worked? Are customers leaving in droves and managers breathing down our necks? How can we make sure we wind up behind therightdoor when the going gets tough? The answer is:craftsmanship.There are two parts to learning craftsmanship: knowledge and work. You must gain the knowledge of principles, patterns, practices, and heuristics that a craftsman knows, and you must also grind that knowledge into your fingers, eyes, and gut by working hard and practicing.I can teach you the physics of riding a bicycle. Indeed, the classical mathematics is relatively straightforward. Gravity, friction, angular momentum, center of mass, and so forth, can be demonstrated with less than a page full of equations. Given those formulae I could prove to you that bicycle riding is practical and give you all the knowledge you needed to make it work. And you'd still fall down the first time you climbed on that bike.Coding is no different. We could write down all the "feel good" principles of clean code and then trust you to do the work (in other words, let you fall down when you get on the bike), but then what kind of teachers would that make us, and what kind of student would that make you?No. That's not the way this book is going to work.Learning to write clean code is hard work. It requires more than just the knowledge of principles and patterns. You must sweat over it. You must practice it yourself, and watch yourself fail. You must watch others practice it and fail. You must see them stumble and retrace their steps. You must see them agonize over decisions and see the price they pay for making those decisions the wrong way.Be prepared to work hard while reading this book. This is not a "feel good" book that you can read on an airplane and finish before you land. This book will make you work, and work hard. What kind of work will you be doing? You'll be reading code--lots of code. And you will be challenged to think about what's right about that code and what's wrong with it. You'll be asked to follow along as we take modules apart and put them back together again. This will take time and effort; but we think it will be worth it.We have divided this book into three parts. The first several chapters describe the principles, patterns, and practices of writing clean code. There is quite a bit of code in these chapters, and they will be challenging to read. They'll prepare you for the second section to come. If you put the book down after reading the first section, good luck to you!The second part of the book is the harder work. It consists of several case studies of ever-increasing complexity. Each case study is an exercise in cleaning up some code--of transforming code that has some problems into code that has fewer problems. The detail in this section is intense. You will have to flip back and forth between the narrative and the code listings. You will have to analyze and understand the code we are working with and walk through our reasoning for making each change we make. Set aside some time becausethis should take you days.The third part of this book is the payoff. It is a single chapter containing a list of heuristics and smells gathered while creating the case studies. As we walked through and cleaned up the code in the case studies, we documented every reason for our actions as a heuristic or smell. We tried to understand our own reactions to the code we were reading and changing, and worked hard to capture why we felt what we felt and did what we did. The result is a knowledge base that desribes the way we think when we write, read, and clean code.This knowledge base is of limited v