OOP - aber richtig
Stefan Priebsch, thePHP.cc
IPC Spring 2009, Berlin

Stefan Priebsch
Co-Founder and Principal Consultant

Disclaimer

„Zum Henker mit
den Regeln! Das
sind sowieso eher
Richtlinien ...“
--Elizabeth Swann,
Pirates of the Caribbean

Ist OOP langsam?

foo() 3.09 µsec
Test::foo() 3.26 µsec
$test->foo() 3.12 µsec
$test = new Test();
$test->foo() 4.03 µsec
Die Benchmarks liefern auf jedem System andere Ergebnisse.

25% langsamer!

1 µsec
im Verhältnis

print ~ 10 µsec
file_get_contents() ~ 30 µsec
mysql_connect() ~ 100 µsec
HTTP GET Request ~ 35,000 µsec
Die Benchmarks liefern auf jedem System andere Ergebnisse.

Achten Sie nicht
#1 auf Performance *
*Ausnahmen bestätigen die Regel

Benutzen Sie
ruhig Objekte

class Something
{
protected $status = array();
public function run(...)
{
if (...) {
…
$this->status['fail'] = $e->getMessage();
} else {
$this->status['skip'] = 'File is unavailable';
}
return $this->status;
}
}

class Something
{
protected $status = array();
public function run(...)
{
if (...) {
…
return new FailResult($e->getMessage());
} else {
return new SkipResult('File is unavailable');
}
}
}

class Result
{
protected $message;
public function __construct($message)
{
$this->message = $message;
}
}
class FailResult extends Result {}
class SkipResult extends Result {}

Wie verdienen Sie
Ihren Lebensunterhalt?

class Something
{
public function doManyThings()
{
… load data …
… perform calculations …
… render HTML output …
… store calculation result ...
}
}

class Something
{
public function doManyThings()
{
$this->loadData();
$this->performCalculations();
$this->renderHtml();
$this->storeResult();
}
protected function loadData()
protected function performCalulations()
protected function renderHtml()
protected function storeResult()
}

class DataLoader
{
public function loadData()
}
class Calculator
{
public function calculateResult()
}
class HtmlRenderer
{
public function render()
}
class StorageManager
{
public function storeResult()
}

Eine Klasse
Eine Verantwortlichkeit

Unterschiedliche
#2 Belange trennen

class DomainObject
{
protected function loadData()
{
$this->data = $this->db->query(...);
}
public function render()
{
$this->loadData();
return HtmlRenderer::createTable($this->data);
}
}

Die anderen
arbeiten lassen

class DomainObject
{
protected function loadData()
{
$this->data = $this->dataManager->query(...);
}
public function render()
{
$this->loadData();
$this->dataRenderer->renderTable($this->data);
}
}

Geheimnisse haben

class SomeDomainObject
{
public function doSomething($a, $b, $c)
{
…
return new SomeResult($x, $y, $z);
}
}

Objekte dumm halten

class SomeDataProcessor
{
public function process($filename)
{
…
$data = file_get_contents($filename);
…
}
}

class SomeDataProcessor
{
public function process($data)
{
…
}
}

Nicht mit
Fremden sprechen

class MeMySelfAndI
{
protected function talk()
{
Stranger::askForACigarette();
}
}

class MeMySelfAndI
{
protected function talk()
{
Stranger::getInstance()->askForACigarette();
}
}

class MeMySelfAndI
{
protected function talkTo($friend)
{
$friend->askForACigarette();
}
}
class Friend
{
public function askForACigarette()
{
return new Cigarette();
}
}

Lose gekoppelte
#3 Klassen erzeugen

Welche Werkzeuge
brauchen Sie, um die
Arbeit zu erledigen?

class DomainObject
{
protected function loadData()
{
$this->data = $this->dataManager->query(...);
}
public function render()
{
$this->loadData();
$this->dataRenderer->renderTable($this->data);
}
}

class DomainObject
{
protected $dataManager;
protected $dataRenderer;
public function __construct($dataManager, $dataRenderer)
{
$this->dataManager = $dataManager;
$this->dataRenderer = $dataRenderer;
}
protected function loadData()
public function render()
}

Injizieren Sie
#4 Abhängigkeiten

Use Dependency
#4 Injection

class Car
{
protected $engine;
protected $wheels = array();
public function __construct()
{
$this->engine = new Engine();
$this->wheels = array(
new Wheel(),
new Wheel(),
new Wheel(),
new Wheel(),
);
}
}

class Car
{
protected $engine;
protected $wheels = array();
public function __construct($engine, array $wheels)
{
$this->engine = $engine;
$this->wheels = $wheels;
}
}

class Car
{
protected $engine;
protected $wheels = array();
public function __construct(Engine $engine, array $wheels)
{
$this->engine = $engine;
$this->wheels = $wheels;
}
}

class Car
{
protected $engine;
protected $wheels = array();
public function __construct(Engine $engine)
{
$this->engine = $engine;
}
public function addWheel(Wheel $wheel)
{
$this->wheels[] = $wheel;
}
}

Komposition statt
#5 Vererbung

Guter OOP-Code kann
immer erweitert werden

#6 Das Problem lösen,
nicht generalisieren

Versuchen Sie
#7 testgetriebene
Entwicklung

Kein Test, kein Feature

Testgetriebene Entwicklung
● Schreiben Sie zuerst einen Unit Test
● Stellen Sie sicher, dass er fehlschlägt
● Schreiben Sie Code, bis der Test
funktioniert
● Fangen Sie wieder von vorne an

require 'PHPUnit/Framework.php';
class TryingTddTest extends PHPUnit_Framework_TestCase
{
}

require 'PHPUnit/Framework.php';
class TryingTddTest extends PHPUnit_Framework_TestCase
{
public function test()
{
}
}

require 'PHPUnit/Framework.php';
class TryingTddTest extends PHPUnit_Framework_TestCase
{
public function test...()
{
}
}

require 'PHPUnit/Framework.php';
class TryingTddTest extends PHPUnit_Framework_TestCase
{
public function testSomething()
{
}
}

Auf die API
fokussieren

require 'PHPUnit/Framework.php';
class TryingTddTest extends PHPUnit_Framework_TestCase
{
public function testAnElePHPantIsBlue()
{
$e = new ElePHPant();
}
}

require 'PHPUnit/Framework.php';
class TryingTddTest extends PHPUnit_Framework_TestCase
{
public function testAnElePHPantIsBlue()
{
$e = new ElePHPant();
$this->assertEquals('#009', $e->getColor());
}
}

Woher soll ich wissen,
was ein ElePHPant ist?

class ElePHPant
{
protected $color = '#009';
public function getColor()
{
return $this->color;
}
}

Du hast gerade einen
blauen ElePHPanten
geschaffen!

class ElePHPant
{
protected $color = '#008';
public function getColor()
{
return $this->color;
}
}

Tut mir leid, aber
dieser ElePHPant
ist nicht blau!

require 'PHPUnit/Framework.php';
class TryingTddTest extends PHPUnit_Framework_TestCase
{
public function testAnElePHPantIsBlue()
{
$e = new ElePHPant();
$this->assertEquals('#009', $e->getColor());
}
public function testAnElePHPantHasPhpLogo()
{
$e = new ElePHPant();
$this->assertTrue($e->getLogo() instanceOf Logo);
}
}

class ElePHPant
{
protected $color = '#009';
public function getColor()
{
return $this->color;
}
public function getLogo()
{
return $this->logo;
}
}

Also, irgendwie hat
dieser ElePHPant
kein Logo ...

require 'PHPUnit/Framework.php';
class TryingTddTest extends PHPUnit_Framework_TestCase
{
public function testAnElePHPantIsBlue()
{
$e = new ElePHPant();
$this->assertEquals('#009', $e->getColor());
}
public function testAnElePHPantHasPhpLogo()
{
$e = new ElePHPant();
$this->assertTrue($e->getLogo() instanceOf Logo);
}
}

class ElePHPant
{
protected $color = '#009';
protected $logo;
public function __construct(Logo $logo)
{
$this->logo = $logo;
}
public function getColor()
{
return $this->color;
}
public function getLogo()
{
return $this->logo;
}
}

require 'PHPUnit/Framework.php';
class TryingTddTest extends PHPUnit_Framework_TestCase
{
public function testAnElePHPantIsBlue()
{
$e = new ElePHPant();
$this->assertEquals('#009', $e->getColor());
}
public function testAnElePHPantHasPhpLogo()
{
$e = new ElePHPant();
$this->assertTrue($e->getLogo() instanceOf Logo);
}
}

require 'PHPUnit/Framework.php';
class TryingTddTest extends PHPUnit_Framework_TestCase
{
public function testAnElePHPantIsBlue()
{
$e = new ElePHPant();
$this->assertEquals('#009', $e->getColor());
}
public function testAnElePHPantHasPhpLogo()
{
$e = new ElePHPant(new Logo());
$this->assertTrue($e->getLogo() instanceOf Logo);
}
}

require 'PHPUnit/Framework.php';
class TryingTddTest extends PHPUnit_Framework_TestCase
{
public function testAnElePHPantIsBlue()
{
$e = new ElePHPant();
$this->assertEquals('#009', $e->getColor());
}
public function testAnElePHPantHasPhpLogo()
{
$e = new ElePHPant(new Logo());
$this->assertTrue($e->getLogo() instanceOf Logo);
$this->assertEquals('PHP', $e->getLogo()->getText());
}
}

class Logo
{
protected $text;
public function __construct($text)
{
$this->text = $text;
}
}

class Logo
{
protected $text;
public function __construct($text)
{
$this->text = $text;
}
...
}

… und Sie
programmieren glücklich
und zufrieden bis ans
Ende aller Tage ...

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