Professional Refactoring

Professional Refactoring International PHP Conference 2009 Spring Edition Mayﬂower GmbH 2009 1

• Senior Developer / Team Lead at Mayﬂower GmbH • Reporting and Rating Apps • QA and PHP 5 Migration consultings • PHP since 1999 (3.0.16) • phpMyFAQ since 2001 Mayﬂower GmbH 2009 2

Who are you? • What are you doing? • What‘s your team size? • Using MVC? • Who‘s using Continous Integration? • PHPUnit? • 80% code coverage? Mayﬂower GmbH 2009 3

Your projects... • What‘s your average project lifetime? • Is there PHP code more than 5 years old? • How many lines of code? • How many change requests per year? • Has there been a specification? • Were all features in the first release as specified? Mayflower GmbH 2009 4

What is Refactoring? „Refactoring is a disciplined technique for restructuring an existing body of code, altering its internal structure without changing its external behavior.“ -Martin Fowler, www.refactoring.com Mayﬂower GmbH 2009 5

Why especially PHP? (c) www.medrehab.com Code Aging! Mayﬂower GmbH 2009 6

A PHP Project in 2000 ... • no coding standards, no PHPDoc • no MVC, no Design Patterns • if you were lucky, someone used a template system • nobody cared about XSS or CSRF a lot of changes in business logics • never got refactored, documentated or even tested ... Mayﬂower GmbH 2009 7

... because it worked! Mayﬂower GmbH 2009 8

In the year 2009 • change requests get more and more expensive • the bug rate is always increasing • the development team motivation is decreasing • requirement changes are almost impossible • new team members need a lot of time to be productive Mayﬂower GmbH 2009 9

Management point of view Costs per Change Request rising frequency Dead end! Beneﬁt per Change Request Mayﬂower GmbH 2009 10

Start refactoring now! Mayﬂower GmbH 2009 11

But hey, stop! Mayﬂower GmbH 2009 12

Don‘t refactor ... • weeks before a important release • only with a lot of junior developers • parallel with development tasks Mayﬂower GmbH 2009 13

Before starting refactoring • define a coding standard • avoids spaghetti code • speeds up maintainability • improves productivity • fix your API specs • complete your documentation Mayflower GmbH 2009 14

During the refactoring... • stay calm • take a lot of good developers and a bunch of juniors • write tests, tests, tests • don‘t let developer refactor their own code • don‘t let junior developers refactor alone Mayﬂower GmbH 2009 15

About Unittests • Testing is essential during refactoring • Problems • most of old code isn‘t „unittestable“ • API breaks during refacotoring • Solution • Selenium tests instead • iterative refactoring Mayﬂower GmbH 2009 16

(c) BMW AG Okay, let‘s start! Mayﬂower GmbH 2009 17

Back to Martin Fowler „Refactoring is a disciplined technique for restructuring an existing body of code, altering its internal structure without changing its external behavior.“ -Martin Fowler, www.refactoring.com Mayﬂower GmbH 2009 18

Forms of refactoring •Renaming •Extraction •Changing signature •Pull up / Pull down Mayﬂower GmbH 2009 19

Renaming /** * Remove a word from the stop word dictionary * * @param integer $id * * @return void */ public function remove($id) { $sql = sprintf(quot;DELETE FROM $this->tablename WHERE id = %d AND lang = '%s'quot;, $id, $this->language); $this->db->query($sql); } Mayﬂower GmbH 2009 20

Renaming /** * Remove a word from the stop word dictionary * * @param integer $stopword_id ID of the stop word * * @return void */ public function remove($stopword_id) { $delete = sprintf(quot;DELETE FROM $this->tablename WHERE id = %d AND lang = '%s'quot;, $stopword_id, $this->language); $this->db->query($delete); } Mayﬂower GmbH 2009 21

Restructuring /** * Remove a word from the stop word dictionary * * @param integer $stopword_id ID of the stop word * * @return void */ public function remove($stopword_id) { $delete = sprintf(quot;DELETE FROM $this->tablename WHERE id = %d AND lang = '%s'quot;, $stopword_id, $this->language); $this->db->query($delete); } Mayﬂower GmbH 2009 22

Restructuring /** * Remove a word from the stop word dictionary * * @param integer $stopword_id ID of the stop word * * @return void */ public function remove($stopword_id) { $delete = sprintf(quot;DELETE FROM %s WHERE id = %d AND lang = '%s'quot;, $this->tablename, $stopword_id, $this->language); $this->db->query($delete); } Mayﬂower GmbH 2009 23

Extraction /** * Remove a word from the stop word dictionary * * @param integer $stopword_id ID of the stop word * * @return void */ public function remove($stopword_id) { $delete = sprintf(quot;DELETE FROM %s WHERE id = %d AND lang = '%s'quot;, $this->tablename, $stopword_id, $this->language); $this->db->query($delete); } Mayﬂower GmbH 2009 24

Extraction public function remove($stopword_id) { $delete = sprintf(quot;DELETE FROM %s WHERE id = %d AND lang = '%s'quot;, $this->tablename, $stopword_id, $this->language); $this->_execute($delete); } private function _execute($query) { return $this->db->query($query) } Mayﬂower GmbH 2009 25

Changing signature /** * Remove a word from the stop word dictionary * * @param integer $id ID of the stop word * * @return void */ public function remove($stopword_id) { $delete = sprintf(quot;DELETE FROM %s WHERE id = %d AND lang = '%s'quot;, $this->tablename, $stopword_id, $this->language); $this->db->query($delete); } Mayﬂower GmbH 2009 26

Changing signature /** * Remove a word from the stop word dictionary * * @param integer $stopword_id ID of the stop word * @param boolean $logging Log removal? Default: false * * @return void */ public function remove($stopword_id, $logging = false) { $delete = sprintf(quot;DELETE FROM %s WHERE id = %d AND lang = '%s'quot;, $this->tablename, $stopword_id, $this->language); if ($logging) { $this->_logAction('removal', $stopword_id); } $this->db->query($delete); } Mayﬂower GmbH 2009 27

Pull up / Pull down x Mayﬂower GmbH 2009 28

Pull up / Pull down x Mayﬂower GmbH 2009 29

Pull up / Pull down x x x Mayﬂower GmbH 2009 30

Tips & Tricks • Always add PHPDoc if it‘s missing • Never trust automatic refactoring of IDEs • Don‘t do refactoring for fun • Write as much unittests as possible Mayﬂower GmbH 2009 31

Any questions? Mayﬂower GmbH 2009 32

Thank you very much for your attention! Thorsten Rinne Mayflower GmbH Mannhardtstraße 6 D-80538 München +49 (0) 89 24 20 54 - 31 thorsten.rinne@mayflower.de Mayflower GmbH 2009 33

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Professional Refactoring

by Mayflower GmbH on May 26, 2009

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Professional Refactoring — Presentation Transcript