Practical Refactoring (NomadPHP)

Every codebase builds up some legacy over time, there is hardly a way around that. But how you handle the legacy is what seperates a good developer from a great developer. Refactoring code should be a part of your every day work, but how to effectively refactor your code? How to ensure the quality of the new code as well as the fact that refactoring code won’t break something elsewhere in your code? During this talk we’ll go into the why, when and how of refactoring.

Transcript

1. Practical Refactoring
   Thursday, August 22, 13
   

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2. Refactoring
   Thursday, August 22, 13
   

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3. Refactoring
   • What is it?
   Thursday, August 22, 13
   

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4. Refactoring
   • What is it?
   • Why would we do it?
   Thursday, August 22, 13
   

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5. Refactoring
   • What is it?
   • Why would we do it?
   • When do we do it?
   Thursday, August 22, 13
   

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6. Refactoring
   • What is it?
   • Why would we do it?
   • When do we do it?
   • How do we do it?
   Thursday, August 22, 13
   

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7. What?
   Thursday, August 22, 13
   

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8. Thursday, August 22, 13
   

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9. Code refactoring is the process of changing a computer
   program's internal structure without modifying its
   external behavior or existing functionality.
   Thursday, August 22, 13
   

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10. Why?
    Thursday, August 22, 13
    

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11. Code is never perfect
    Thursday, August 22, 13
    

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12. Thursday, August 22, 13
    

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13. Thursday, August 22, 13
    

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14. Code quality
    Thursday, August 22, 13
    

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15. Code quality
    • Lessen complexity
    Thursday, August 22, 13
    

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16. Code quality
    • Lessen complexity
    • Increase readability
    Thursday, August 22, 13
    

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17. Code quality
    • Lessen complexity
    • Increase readability
    • Increase maintainability
    Thursday, August 22, 13
    

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18. Code quality
    • Lessen complexity
    • Increase readability
    • Increase maintainability
    • Upgrade performance
    Thursday, August 22, 13
    

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19. Code quality
    • Lessen complexity
    • Increase readability
    • Increase maintainability
    • Upgrade performance
    • Increase stability
    Thursday, August 22, 13
    

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20. Functionality
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21. Functionality
    • New functionality
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22. Functionality
    • New functionality
    • Updated functionality
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23. Thursday, August 22, 13
    

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24. DON’T...
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25. DON’T...
    • Just beautify your code
    Thursday, August 22, 13
    

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26. DON’T...
    • Just beautify your code
    • Refactor because of refactoring
    Thursday, August 22, 13
    

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27. Selling refactoring to
    your manager/customer
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28. What’s in it for them?
    Thursday, August 22, 13
    

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29. What’s in it for them?
    • Less bugs
    Thursday, August 22, 13
    

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30. What’s in it for them?
    • Less bugs
    • Faster development
    Thursday, August 22, 13
    

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31. What’s in it for them?
    • Less bugs
    • Faster development
    • It is part of the process
    Thursday, August 22, 13
    

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32. Example
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33. Example
    if ($order) {
    if ( ! $order->retryPossible()) {
    throw new BadRequestHttpException('Order already exists for ShoppingCart');
    }
    }
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34. Example
    if ($order) {
    if ( ! $order->retryPossible()) {
    throw new BadRequestHttpException('Order already exists for ShoppingCart');
    }
    }
    public function isOpen()
    {
    return $this->getOrder() === null;
    }
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35. Example
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36. Example
    public function isOpen()
    {
    return (
    $this->getOrder() === null ||
    $this->getOrder()->retryPossible() === true
    );
    }
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37. Thursday, August 22, 13
    

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38. A good read
    http://robots.thoughtbot.com/post/2685998010/ongoing-refactoring-and-client-work
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39. Thursday, August 22, 13
    

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40. When?
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41. Continuously
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42. Really
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43. Continuously
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44. Continuously
    • NOT: Always
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45. Continuously
    • NOT: Always
    • NOT: Immediately
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46. Continuously
    Thursday, August 22, 13
    

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47. Continuously
    • Your code gets better, one step at a time
    Thursday, August 22, 13
    

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48. Continuously
    • Your code gets better, one step at a time
    • You don’t spend ages on refactoring, it’s
    part of the project
    Thursday, August 22, 13
    

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49. How?
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50. Isolation
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51. Isolation
    • Small, independant classes and methods
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52. Isolation
    • Small, independant classes and methods
    • Class or method too big? refactor again!
    Thursday, August 22, 13
    

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53. mysql_connect('127.0.0.1', 'root');
    mysql_select_db('refactoring');
    $newsSQL = "SELECT * FROM NEWS ORDER BY published_at DESC";
    $result = mysql_query($newsSQL);
    while($row = mysql_fetch_assoc($result))
    {
    echo $row['published_at'] . ': ' . $row['title'].'
    ';
    echo nl2br($row['message']) . '
    
    ';
    }
    Thursday, August 22, 13
    

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54. Thursday, August 22, 13
    

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55. require_once('config.php');
    $db = new PDO('mysql:dbname='.$db_name.';host='.$db_server,
    $db_user, $db_pass);
    $newsSQL = "SELECT * FROM NEWS ORDER BY published_at DESC";
    $stmt = $db->prepare($newsSQL);
    $stmt->execute();
    while($row = $stmt->fetch(PDO::FETCH_ASSOC))
    {
    echo $row['published_at'] . ': ' . $row['title'].'
    ';
    echo nl2br($row['message']) . '
    
    ';
    }
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56. $db_server = '127.0.0.1';
    $db_user = 'root';
    $db_pass = '';
    $db_name = 'refactoring';
    require_once('config.php');
    $db = new PDO('mysql:dbname='.$db_name.';host='.$db_server,
    $db_user, $db_pass);
    $newsSQL = "SELECT * FROM NEWS ORDER BY published_at DESC";
    $stmt = $db->prepare($newsSQL);
    $stmt->execute();
    while($row = $stmt->fetch(PDO::FETCH_ASSOC))
    {
    echo $row['published_at'] . ': ' . $row['title'].'
    ';
    echo nl2br($row['message']) . '
    
    ';
    }
    Thursday, August 22, 13
    

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57. Thursday, August 22, 13
    

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58. class NewsRepository
    {
    private $db;
    public function __construct($db)
    {
    $this->db = $db;
    }
    public function getAllNews()
    {
    $newsSQL = "SELECT * FROM NEWS ORDER BY published_at
    DESC";
    $stmt = $this->db->prepare($newsSQL);
    $stmt->execute();
    return $stmt->fetchAll(PDO::FETCH_ASSOC);
    }
    }
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59. require_once('config.php');
    require_once('NewsRepository.php');
    $db = new PDO('mysql:dbname='.$db_name.';host='.$db_server,
    $db_user, $db_pass);
    $newsRepo = new NewsRepository($db);
    $news = $newsRepo->getAllNews();
    foreach($news as $row)
    {
    echo $row['published_at'] . ': ' . $row['title'].'
    ';
    echo nl2br($row['message']) . '
    
    ';
    }
    Thursday, August 22, 13
    

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60. Thursday, August 22, 13
    

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61. Thursday, August 22, 13
    

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62. Thursday, August 22, 13
    

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63. Tests
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64. Tests
    • Tests are contracts and verifications
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65. Tests
    • Tests are contracts and verifications
    • Contract: Code should do what is tested
    Thursday, August 22, 13
    

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66. Tests
    • Tests are contracts and verifications
    • Contract: Code should do what is tested
    • Verification: Does it do what is tested?
    Thursday, August 22, 13
    

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67. Tests
    • Tests are contracts and verifications
    • Contract: Code should do what is tested
    • Verification: Does it do what is tested?
    • Don’t change the tests
    Thursday, August 22, 13
    

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68. Tests
    • Tests are contracts and verifications
    • Contract: Code should do what is tested
    • Verification: Does it do what is tested?
    • Don’t change the tests
    • Just expand the test
    Thursday, August 22, 13
    

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69. class NewsRepositoryTest extends PHPUnit_Framework_TestCase
    {
    $private $MockDb;
    public function setUp()
    {
    // here we set up the mock class
    $this->MockDb = new MockDb();
    }
    public function testGetAllNews()
    {
    $newsRepo = new NewsRepository($this->MockDb);
    // mock repo returns 2 newsitems
    $news = $newsRepo->getAllNews();
    $this->assertEquals(2, count($news));
    }
    }
    Thursday, August 22, 13
    

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70. public function getAllNews($limit = null)
    {
    $newsSQL = "SELECT * FROM NEWS ORDER BY published_at DESC";
    if ( ! is_null($limit)) {
    $newsSQL .= " LIMIT 0, " . $limit;
    }
    $stmt = $this->db->prepare($newsSQL);
    $stmt->execute();
    return $stmt->fetchAll(PDO::FETCH_ASSOC);
    }
    Thursday, August 22, 13
    

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71. public function testGetAllNews()
    {
    $newsRepo = new NewsRepository($this->MockDb);
    // mock repo returns 2 newsitems
    $news = $newsRepo->getAllNews();
    $this->assertEquals(2, count($news));
    // new functionality: limit the newsitems
    $news = $newsRepo->getAllNews(1);
    $this->assertEquals(1, count($news));
    }
    Thursday, August 22, 13
    

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72. When you change your
    test...
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73. You change the
    behaviour of your code
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74. Tests
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75. Tests
    • Untested code?
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76. Tests
    • Untested code?
    • Write tests before refactoring if possible
    Thursday, August 22, 13
    

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77. Tests
    • Untested code?
    • Write tests before refactoring if possible
    • Write tests during refactoring
    Thursday, August 22, 13
    

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78. Tests
    • Untested code?
    • Write tests before refactoring if possible
    • Write tests during refactoring
    • Tested code?
    Thursday, August 22, 13
    

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79. Tests
    • Untested code?
    • Write tests before refactoring if possible
    • Write tests during refactoring
    • Tested code?
    • Expand those tests
    Thursday, August 22, 13
    

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80. Your IDE can help
    • Most IDE’s have refactoring support
    • Scan for usage of methods and classes
    • http://qafoo.com/blog/
    041_refactoring_browser.html
    Thursday, August 22, 13
    

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81. So, refactoring
    Thursday, August 22, 13
    

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82. So, refactoring
    • What is it?
    Thursday, August 22, 13
    

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83. So, refactoring
    • What is it?
    • Why would we do it?
    Thursday, August 22, 13
    

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84. So, refactoring
    • What is it?
    • Why would we do it?
    • When do we do it?
    Thursday, August 22, 13
    

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85. So, refactoring
    • What is it?
    • Why would we do it?
    • When do we do it?
    • How do we do it?
    Thursday, August 22, 13
    

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86. Thank you!
    • https://joind.in/talk/view/8978
    • http://php.ingewikkeld.net/
    Thursday, August 22, 13
    

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