Clean Code

Clean Code

Presentation of the Uncle Bob's Book.

1Thursday, December 1, 11

The Speaker

• Brice Argenson– Full Professor in Java and Web Technologies

• Professional Experiences :

• Certifications :

– Bug Out PC– ADF– Adullact– Webpulser

– Audaxis– Groupe Open– Atos Worldline– Xebia IT

– SCJP 6– SCWCD 5

– MCP – Exam 70-316

[email protected] @bargenson


Agenda

• Software Craftsmanship

• Why Clean Code ?

• Tips & Tricks to write Clean Code

• References


SOFTWARE CRAFTSMANSHIPWhat is that ?


5


6


WHY CLEAN CODE ?Bad Code VS. Clean Code



Bad Code

• Bad Code killed some companies– Rushed the product to market– More and more features– Worse and worse code– Code unmanageable

• We all wrote bad code– Trying to go fast ?– We were in a rush ?– We’ll clean it up later…



The Cost of Bad Code

• Do you have been slowed down by messy code ?

• More & more mess è Less & less productivity

• When productivity became terrible è Redesign

• And again…• And again…


Whose Fault ?

• The customer ?– The requirements change too much ?

• The managers ?– The deadlines are too short ?

• It is mainly the developer fault !– The others look to us for the information they need– The doctor knows more than the patient about the risks

[…]

• Be professionals !


What is Clean Code ?

• What is Clean Code for you ?– It is working ?– It is efficient ?– It is short ?

• Clean Code is easy to read !

• We are authors !


What is Clean Code ?

• The Boy Scout Rule :– Leave the campground cleaner than you found it.

• Refactor your code !

• Write tests !– Test Driven Development


GET YOUR HANDS DIRTY !How to write Clean Code ?


Meaningful Names

• What is the purpose of this code ?


Meaningful Names

• And what do you think of this code ?


Meaningful Names

• Use Intention-Revealing Names


Meaningful Names

• What about Hungarian Notation ?


Meaningful Names

• What if one day we change the type ?

• Hungarian Notation make it harder to change the name or type of a variable, function or class


Meaningful Names

• What about Member Prefixes ?– Example: m_firstName

• Classes and functions should be small enough that you don’t need them

• IDE highlights or colorizes members !

• Prefixes become unseen clutter


Functions

• What do you think about this method ?– FitNesse - commit 3bec390e6f

• And now ?– FitNesse - commit 7491001db7

• What has changed ?


https://github.com/unclebob/fitnesse/blob/3bec390e6f8e9e341149b7d060551a92b93d3154/src/fitnesse/html/HtmlUtil.java

https://github.com/unclebob/fitnesse/blob/3bec390e6f8e9e341149b7d060551a92b93d3154/src/fitnesse/html/HtmlUtil.java

https://github.com/unclebob/fitnesse/blob/7491001db74ad1b577e3e3e44e3b87c93e881c02/src/fitnesse/html/SetupTeardownIncluder.java

https://github.com/unclebob/fitnesse/blob/7491001db74ad1b577e3e3e44e3b87c93e881c02/src/fitnesse/html/SetupTeardownIncluder.java

Functions

• Small !– Not bigger than a screen full

• Correct in the eighties (24 x 80)

– Should be transparently obvious– Indent level should not be greater than one or two

• Do one thing !– Your function is divided into section ?

• You can divide it !

• The Stepdown Rule !– We want the code to read like a top-down narrative


Functions

• Function arguments ?– Niladic

• The ideal number

– Monadic• A good number

– Dyadic• A good number

– Triadic• Should be avoided

– Polyadic• Do you need to wrap the arguments into a new type ?


Error Handling

• What do you think about this code ?


Error Handling

• Prefer exceptions to returning error codes


Error Handling

• And what do you think about this code ?


Error Handling

• For you what is the most common exception ?– NPE !

• How to avoid it ?

28


Error Handling


29


Error Handling

• Don’t return Null !

30


Error Handling


31


Error Handling

• How to make code look like that ?

• Special Case object !

32


Side Effects

• Consider the following class :

33


Side Effects

• Consider the following code :

• Do you see the problem ?

34


Side Effects

• To protect the internals of a Period instance from this sort of attack:

– You must make defensive copy of each mutable parameter to the constructor !

35


Side Effects

• Inheritance is a powerful way to achieve code reuse– But not always the best !

• Inheritance from ordinary concrete classes across package boundaries is dangerous !

• Unlike method invocation, inheritance violates encapsulation

36


Side Effects

37


Side Effects

• What this code display ?

38


Side Effects

39


Side Effects

40


Side Effects

• Design of the InstrumentedSet is extremely flexible :– Implement the Set interface– Receive an argument also of type Set

• With inheritance, we could work only with HashSet

• With composition, we can work with any Set implementation !

41


Side Effects

• Favor composition over inheritance !

42


REFERENCESDo you want to read more about the subject ?

43


Books

44

Clean CodeA Handbook of Agile Software Craftsmanship

Robert C. Martin (aka. Uncle Bob)

Prentice Hall editions


Books

45

Effective JavaSecond Edition

Joshua Bloch

Addison Wesley editions


Links

• Sign the Manifesto – http://manifesto.softwarecraftsmanship.org

• Software Craftsmanship en pratique - Xebia– http://blog.xebia.fr/2011/01/31/software-craftsmanship-

en-pratique/

• The Clean Coder - Uncle Bob blog– http://thecleancoder.blogspot.com/

46


http://manifesto.softwarecraftsmanship.org/

http://manifesto.softwarecraftsmanship.org/

http://blog.xebia.fr/2011/01/31/software-craftsmanship-en-pratique/




http://thecleancoder.blogspot.com/

http://thecleancoder.blogspot.com/

Clean Code

Technology

side effects

error handling

bad code

meaningful names

clean code

code

functions

function