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
2. Refactoring • What is it? • Why would we do it? • When do we do it? • How do we do it?
3. What?
5. Code refactoring is the process of changing a computer program's internal structure without modifying its external behavior or existing functionality.
6. Why?
7. Code is never perfect
10. Code quality • Lessen complexity • Increase readability • Increase maintainability • Upgrade performance • Increase stability
11. Functionality • New functionality • Updated functionality
13. DON’T... • Just beautify your code • Refactor because of refactoring
14. Selling refactoring to your manager/customer
15. What’s in it for them? • Less bugs • Faster development • It is part of the process
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 ); }
18. A good read http://robots.thoughtbot.com/post/2685998010/ongoing-refactoring-and-client-work
20. When?
21. Continuously
22. Really
23. Continuously • NOT: Always • NOT: Immediately
24. Continuously • Your code gets better, one step at a time • You don’t spend ages on refactoring, it’s part of the project
25. How?
26. Isolation • Small, independant classes and methods • Class or method too big? refactor again!
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'] . ': ' . $row['title'].'<br />'; echo nl2br($row['message']) . '<br /><br />'; }
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'] . ': ' . $row['title'].'<br />'; echo nl2br($row['message']) . '<br /><br />'; }
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); } }
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'] . ': ' . $row['title'].'<br />'; echo nl2br($row['message']) . '<br /><br />'; }
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
37. <?php 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)); } }
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); }
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)); }
40. When you change your test...
41. You change the behaviour of your code
42. Tests • Untested code? • Write tests before refactoring if possible • Write tests during refactoring • Tested code? • Expand those tests
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
44. What about my legacy?
45. So, refactoring • What is it? • Why would we do it? • When do we do it? • How do we do it?
46. Thank you! • https://joind.in/11795 • http://php.ingewikkeld.net