Slides des conférences publiques hébergées par SUPINFO (http://www.supinfo.com) données en Octobre 2011 à Nantes et Novembre 2011 à Montréal.

1. Clean Code
Presentation of the Uncle Bob's Book.
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2. The Speaker
• Brice Argenson
– Full Professor in Java and Web Technologies
• Professional Experiences :
– Bug Out PC – Audaxis
– ADF – Groupe Open
– Adullact – Atos Worldline
– Webpulser – Xebia IT
• Certifications :
– SCJP 6 – MCP – Exam 70-316
– SCWCD 5
brice.argenson@supinfo.com @bargenson
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3. Agenda
• Software Craftsmanship
• Why Clean Code ?
• Tips & Tricks to write Clean Code
• References
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4. What is that ?
SOFTWARE CRAFTSMANSHIP
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5. 5
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6. 6
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7. Bad Code VS. Clean Code
WHY CLEAN CODE ?
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8. Thursday, December 1, 11 8

9. 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…
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10. Thursday, December 1, 11 10

11. 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…
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12. 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 !
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13. 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 !
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14. What is Clean Code ?
• The Boy Scout Rule :
– Leave the campground cleaner than you found it.
• Refactor your code !
• Write tests !
– Test Driven Development
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15. How to write Clean Code ?
GET YOUR HANDS DIRTY !
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16. Meaningful Names
• What is the purpose of this code ?
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17. Meaningful Names
• And what do you think of this code ?
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18. Meaningful Names
• Use Intention-Revealing Names
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19. Meaningful Names
• What about Hungarian Notation ?
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20. 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
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21. 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
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22. Functions
• What do you think about this method ?
– FitNesse - commit 3bec390e6f
• And now ?
– FitNesse - commit 7491001db7
• What has changed ?
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23. 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
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24. 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 ?
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25. Error Handling
• What do you think about this code ?
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26. Error Handling
• Prefer exceptions to returning error codes
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27. Error Handling
• And what do you think about this code ?
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28. Error Handling
• For you what is the most common exception ?
– NPE !
• How to avoid it ?
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29. Error Handling
• What do you think about this code ?
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30. Error Handling
• Don’t return Null !
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31. Error Handling
• What do you think about this code ?
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32. Error Handling
• How to make code look like that ?
• Special Case object !
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33. Side Effects
• Consider the following class :
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34. Side Effects
• Consider the following code :
• Do you see the problem ?
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35. 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 !
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36. 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
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37. Side Effects
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38. Side Effects
• What this code display ?
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39. Side Effects
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40. Side Effects
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41. 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 !
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42. Side Effects
• Favor composition over inheritance !
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43. Do you want to read more about the subject ?
REFERENCES
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44. Books
Clean Code
A Handbook of Agile Software Craftsmanship
Robert C. Martin (aka. Uncle Bob)
Prentice Hall editions
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45. Books
Effective Java
Second Edition
Joshua Bloch
Addison Wesley editions
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46. 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/
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