Seven StepsSeven Stepsto Better OOP Code to Better OOP Code

Stefan PriebschStefan Priebsch

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Stefan PriebschStefan PriebschCo-Founder and Principal ConsultantCo-Founder and Principal Consultant

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DisclaimerDisclaimer

„„Hang the rules. Hang the rules. They're more like They're more like guidelines anyway.“guidelines anyway.“

--Elizabeth Swann,--Elizabeth Swann,Pirates of the CaribbeanPirates of the Caribbean

Is OOP slow?Is OOP slow?

The usual disclaimer for benchmarks applies!The usual disclaimer for benchmarks applies!

foo() foo() 3.09 µsec3.09 µsec

Test::foo() 3.26 µsec

$test->foo() 3.12 µsec

$test = new Test();$test->foo() 4.03 µsec

25% slower!25% slower!

1 µsec1 µsec

The usual disclaimer for benchmarks applies!The usual disclaimer for benchmarks applies!

print ~ 10 µsec

file_get_contents() ~ 30 µsec

mysql_connect() ~ 100 µsec

HTTP GET Request ~ 35,000 µsec

I/O is whereI/O is wherethe action is.the action is.

OOP isOOP isfast enough.fast enough.

Do not care about Do not care about performanceperformance**

*Some restrictions may apply.*Some restrictions may apply.

#1#1

WhatWhatdo youdo youdo for ado for aliving?living?

class Something{ public function doWork() { … 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()}

Clearly separate Clearly separate different concernsdifferent concerns#2#2

One ResponsibilityOne Responsibility

class SomeObject{ protected function loadData() { $this->data = $this->db->query(...); }

public function render() { $this->loadData(); return HtmlRenderer::createTable($this->data); }}

Let othersLet othersdo the work.do the work.

class CrystalBall{ public function predictLottoNumbers($a, $b, $c) { …

return new LottoNumbers(...); }}

Focus on the APIFocus on the API#3#3

Interface vs. Interface vs. ImplementationImplementation

Keep secretsKeep secrets

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

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

class Person{ protected function talkTo(Friend $friend) { $friend->askForACigarette(); }}

class Friend{ public function askForACigarette() { return new Cigarette(); }}

Do not talkDo not talkto strangers.to strangers.

Create loosely Create loosely coupled classescoupled classes#4#4

Make Make dependencies dependencies

explicit.explicit.

class SomeObject{ protected function loadData() { $this->data = $this->db->query(...); }

public function render() { $this->loadData(); return HtmlRenderer::createTable($this->data); }}

class SomeObject{ protected function loadData() { $this->data = $this->db->query(...); }

public function render(Renderer $renderer) { $this->loadData(); return $this->renderer->createTable($this->data); }}

class SomeObject{ protected function loadData(DbGateway $db) { $this->data = $db->query(...); }

public function render(Renderer $renderer) { $this->loadData(); return $renderer->createTable($this->data); }}

class SomeObject{ public function __construct(DbGateway $db, Renderer $r) { $this->db = $db; $this->renderer = $r; }

...}

Use dependency Use dependency injectioninjection#5#5

class Engine{ public function start(); public functoin stop(); public function goFaster($amount); public function goSlower($amount);}

class Car extends Engine{ ...}

class SteeringWheel{ public function turnRight($degrees); public function turnLeft($degree);}

class Car extends Engine extends SteeringWheel{ ...}

Multiple inheritance?Multiple inheritance?

EngineEngine

EngineEngine++

Steering WheelSteering Wheel

EngineEngine++

Steering WheelSteering Wheel++

SeatSeat

CombineCombineobjects.objects.

CarCar

EngineEngine

SeatSeat

SteeringSteeringWheelWheel

class Car{ protected $engine; protected $steeringWheel; protected $frontSeat;

public function __construct() { $this->engine = new Engine(); $this->steeringWheel = new SteeringWheel(); $this->frontSeat = new Seat(); }}

class Car{ public function __construct(Engine $engine, SteeringWheel $steeringWheel, Seat $seat) { $this->engine = $engine; $this->steeringWheel = $steeringWheel; $this->frontSeat = $seat; }}

$engine = new Engine();$steeringWheel = new SteeringWheel();$seat = new Seat();

$car = new Car($engine, $steeringWheel, $seat);

$engine = new SuperStrongEngine();$steeringWheel = new FancySteeringWheel();$seat = new MichaelSchuhmacherRacingSeat();

$car = new Car($engine, $steeringWheel, $seat);

Favour composition Favour composition over inheritanceover inheritance#6#6

AvoidAvoidinheritance.inheritance.

SuperglobalsSuperglobalsConstantsConstants

SessionSession

ConfigurationConfigurationDatabaseDatabase

WebserviceWebservice

Class to TestClass to Test

If it's not tested,If it's not tested,it does not existit does not exist

Make it easyMake it easyto (unit) testto (unit) test#7#7

Fewer Fewer dependencies.dependencies.

TestableTestable==

MaintainableMaintainable

TestableTestable==

ExtensibleExtensible

Thank you.Thank you.

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