BE CLEAN, MY FRIEND A modest review of Robert C. Martin “Clean Code, A handbook of Agile Craftmanship” book. 11/10/13 @GDGBarcelona #devfestbcn with @pensashure

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BE CLEAN, MY FRIEND
A modest review of
Robert C. Martin
“Clean Code, A handbook of Agile Craftmanship”
book

2. { THANK YOU ALL }
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3. { DO WE NEED TO CODE BETTER? }
{ Motivation }
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4. { MAIN QUESTION: WHY? }
1. You want to be a good
programmer
1. You want to be better
programmer
1. You like being part of
best teams.
{ Motivation }
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5. { REALLY ?? ?? }
int d; // elapsed time in days
or
int elapsedTimeInDays;
int daysSinceCreation;
int fileAgeInDays;
{ Motivation }
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6. { WHAT IS CLEAN CODE ?? }
Complex things
=
composition of simple things.
Set of techniques to help us achieve
complexity from simplicity.
{ Concepts }
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7. { TABLE OF CONTENTS }
❏ Baptism
❏ What & how are you building?
❏ Unexpected things
❏ What’s inside?
❏ Are you testing?
❏ Before development
❏ Tell me a (beautiful) story
❏ Last, but not least
❏ Recommended readings
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8. { BAPTISM }
/* NAMING GUIDELINES */
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9. /* USE INTENTION-REVEALING NAMES */
{ Baptism - Naming guidelines }
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10. /* USE INTENTION-REVEALING NAMES */
METHOD CODE
{ Baptism - Naming guidelines }
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11. /* USE PRONOUNCEABLE NAMES */
{ Baptism - Naming guidelines }
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12. /* CLASSES AND METHODS */
❏ Classes should have noun or noun phrase names
❏ payment
❏ Page
❏ singleUser
❏ BankAccount
❏ myObj
❏ Methods should have verbs or verbs phrase names
❏ postPayment
❏ checkPaymentTransfered
❏ delPag
❏ save
❏ checkUserProfileAllowPaymentByCreditCard
{ Baptism - Naming guidelines }
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13. /* CLASSES AND METHODS */
{ Baptism - Naming guidelines }
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14. { WHAT & HOW ARE YOU
BUILDING }
/* CLASSES & METHODS */
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15. /* POLYMORPHISM OVER IF/ELSE */
http://www.antiifcampaign.com/
{ Classes & methods }
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16. /* FUNCTIONS SHOULD DO ONE THING*/
{ Classes & methods }
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17. /* OUTPUT ARGUMENTS */
{ Classes & methods }
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18. { UNEXPECTED THINGS }
/* ERROR HANDLING */
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19. /* PREFER EXCEPTIONS TO RETURN CODES
*/
{ Error handling }
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20. /* PREFER EXCEPTIONS TO RETURN CODES
*/
{ Error handling }
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21. /* DON’T RETURN NULL */
{ Error handling }
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22. /* DON’T PASS NULL */
{ Error handling }
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23. { WHAT IS INSIDE? }
/* OBJECTS & DATA STRUCTURES */
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24. /* HIDE STRUCTURES */
{ Objects & data structures }
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25. /* DATA ABSTRACTION */
{ Objects & data structures }
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26. /* DATA TRANSFER OBJECTS */
{ Objects & data structures }
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27. /* LAW OF DEMETER */
❏ Each unit should have only limited knowledge about
other units: only units "closely" related to the current
unit.
❏ Each unit should only talk to its friends; don't talk to
strangers.
❏ Only talk to your immediate friends
{ Objects & data structures }
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28. /* LAW OF DEMETER */
❏ A method 'm' of a class 'C' may only invoke the
methods of the following kinds of elements:
❏ 'C' itself
❏ 'm's parameters
❏ Any objects created/instantiated within 'm'
❏ ‘C’'s direct component objects
❏ A global variable, accessible by 'C', in the scope
of 'm'
{ Objects & data structures }
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29. /* LAW OF DEMETER */
{ Objects & data structures }
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30. { ARE YOU TESTING ? }
/* UNIT TESTING ! */
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31. /* USE A COVERAGE TOOL */
Cobertura
Sonar
{ Unit testing }
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32. /* TAKE CARE OF TESTS */
❏ Don’t skip trivial tests…
❏ But don’t do ONLY trivial tests!!!
❏ Tests the limits/boundaries of the conditions!
❏ One assert per test!
{ Unit testing }
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33. /* KEEP TEST CLEAN */
{ Unit testing }
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34. { BEFORE DEVELOPMENT ... }
/* DESIGN */
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35. /* PRINCIPLES & ADVICES */
❏ Don’t repeat yourself (DRY): duplication is evil!
{ Design }
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36. /* PRINCIPLES & ADVICES */
❏ Runs all the tests
❏ They will help you
❏ Writing tests leads to better designs!
❏ Refactoring = incrementally improvement
❏ Successive refinement
❏ Separation of main (construction objects <> use)
{ Design }
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37. /* FACTORIES */
{ Design }
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38. /* DEPENDENCY INJECTION */
With Dependency Injection
(Low dependency with the Interface
and Implementation, because the
Assembler does the job)
Without Dependency Injection
(Hard dependency with the Interface
and Implementation)
{ Design }
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39. { TELL ME A (BEAUTIFUL) STORY }
/* COMMENTS */
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40. /* EXPLAIN YOURSELF IN CODE */
{ Comments }
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41. /* GOOD COMMENTS */
❏ Legal comments
❏ Informative comments
❏ Explanation of Intent
❏ Warning of Consequences
❏ TODOs
❏ JavaDocs
{ Comments }
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42. /* BAD COMMENTS */
/**
* @param title The title
* @param author The author
*/
/**
* Returns the day of the month
*
* @return the day of the month
*/
public int getDayOfMonth() {
return dayOfMonth;
}
/**
* CHANGES
* ------------* 02-Oct-2001 Reorganize process
* 15-Nov-2001 Added new Purchaser type
* 21-Nov-2001 Some customer objects arrive without city set
*/
{ Comments }
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43. { LAST, BUT NOT LEAST }
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44. /* THINK ABOUT IT */
❏ This is not a mantra
❏ (Try to) know your environment!
❏ Code is always live
❏ Refactor & test, test & refactor
{ Last, but not least }
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45. /* BE CAREFUL */
Always code as if the guy who ends up
maintaining your code will be a violent
psychopath who knows where you live.
John F. Woods
{ Last, but not least }
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46. { DO YOU LIKE IT ?? READ IT ... }
Clean Code, A Handbook of Agile Software Craftmanship
Robert C. Martin
Publication date: August 11, 2008
ISBN-13: 978-0132350884
{ ... OR ... WATCH IT !! }
http://cleancoders.com/
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47. { RECOMMENDED READINGS }
Effective Java (2nd edition)
Joshua Bloch
Publication Date: May 28, 2008
ISBN-13: 978-0321356680
Thinking in Java (4rd edition)
Bruce Eckel
Publication Date: February 20, 2006
ISBN-13: 978-0131872486
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48. { RECOMMENDED READINGS }
Design Patterns: Elements of Reusable
Object-Oriented Software
Erich Gamma, Richard Helm, Ralph Johnson,
John Vlissides
Publication Date: November 10, 1994
ISBN-13: 978-0201633610
Refactoring: Improving the Design
of Existing Code
Martin Fowler, Kent Beck, John Brant,
William Opdyke, Don Roberts
Publication Date: July 8, 1999
ISBN-13: 978-0201485677
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49. Thank you !
public static void main (String[] args) {
Author bookAuthor = new Author (“Robert”,”C.Martin”);
String bookTitle = “Clean Code, A handbook of Agile
Craftmanship”;
Book cleanCodeBook = new Book(bookTitle, bookAuthor);
Engineer esteve = new Engineer(“@pensashure”);
Engineer nacho = new Engineer(“@icougil”);
Review review = new Review(cleanCodeBook);
review.perform( Arrays.asList(esteve, nacho) );
System.out.println(“THANKS FOR YOUR ATTENTION”);
}
@BarcelonaJUG
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