Practical Refactoring (PHPNW14)

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Practical Refactoring

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

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What?

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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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Why?

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Code is never perfect

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

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Functionality • New functionality • Updated functionality

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

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Selling refactoring to your manager/customer

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

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

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When?

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Continuously

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Really

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Continuously • NOT: Always • NOT: Immediately

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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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How?

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

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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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$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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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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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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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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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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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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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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When you change your test...

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You change the behaviour of your code

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

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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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What about my legacy?

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

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