Practical Refactoring (PHPNW14)

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
   

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2. Refactoring
   • What is it?
   
   • Why would we do it?
   
   • When do we do it?
   
   • How do we do it?
   

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3. What?
   

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5. Code refactoring is the process of changing a computer
   program's internal structure without modifying its
   external behavior or existing functionality.
   

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6. Why?
   

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7. Code is never perfect
   

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10. Code quality
    • Lessen complexity
    
    • Increase readability
    
    • Increase maintainability
    
    • Upgrade performance
    
    • Increase stability
    

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11. Functionality
    • New functionality
    
    • Updated functionality
    

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13. DON’T...
    • Just beautify your code
    
    • Refactor because of refactoring
    

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14. Selling refactoring to
    your manager/customer
    

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15. What’s in it for them?
    • Less bugs
    
    • Faster development
    
    • It is part of the process
    

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16. Example
    if ($order) {
    if ( ! $order->retryPossible()) {
    throw new BadRequestHttpException('Order already exists for ShoppingCart');
    }
    }
    public function isOpen()
    {
    return $this->getOrder() === null;
    }
    public function isOpen()
    {
    return (
    $this->getOrder() === null ||
    $this->getOrder()->retryPossible() === true
    );
    }
    

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18. A good read
    http://robots.thoughtbot.com/post/2685998010/ongoing-refactoring-and-client-work
    

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20. When?
    

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21. Continuously
    

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22. Really
    

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23. Continuously
    • NOT: Always
    
    • NOT: Immediately
    

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

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25. How?
    

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26. Isolation
    • Small, independant classes and methods
    
    • Class or method too big? refactor again!
    

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27. 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']) . '
    
    ';
    }
    

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29. $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']) . '
    
    ';
    }
    

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31. 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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32. 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']) . '
    
    ';
    }
    

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36. 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
    

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37. 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));
    }
    }
    

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38. 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);
    }
    

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39. 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));
    }
    

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40. When you change your
    test...
    

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41. You change the
    behaviour of your code
    

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42. Tests
    • Untested code?
    
    • Write tests before refactoring if possible
    
    • Write tests during refactoring
    
    • Tested code?
    
    • Expand those tests
    

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43. 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
    

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44. What about my legacy?
    

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45. So, refactoring
    • What is it?
    
    • Why would we do it?
    
    • When do we do it?
    
    • How do we do it?
    

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46. Thank you!
    • https://joind.in/11795
    
    • http://php.ingewikkeld.net
    

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