design attern in php

Design pattern in PHP

Filippo De Santis - fd@ideato.it - @filippodesantis

Design pattern in PHP

Web developer

Working in @ideato since 2009

XP and Kanban user

Design pattern in PHPWhat is a design pattern?

Design pattern in PHP

“Each pattern describes a problem which occurs over and over again in our environment, and then describes the core of the solution to that problem, in such a way that you can use this solution a million times over, without ever doing it

the same way twice”

Christopher Alexander

What is a design pattern?

Design pattern in PHP

“A pattern is a [general] solution to a problem in a context”

Gang of four

What is a design pattern?

Design pattern in PHP

Name

Used to describe a design problem, its solution and its consequences in a word or two

Elements of a design pattern

Design pattern in PHP

Problem

Describes when to apply a pattern

Elements of a design pattern

Design pattern in PHP

Solution

Describes the elements that make up the design, their relationships, responsibilities, and collaborations

Elements of a design pattern

Design pattern in PHP

Consequences

The results and trade-offs of applying the pattern

Elements of a design pattern

Design pattern in PHPSingleton

Design pattern in PHPSingleton

Ensures that a class has one instance onlyProvides a global point of access to it

Design pattern in PHPSingleton

Access controlOnly one instance

YES!

Design pattern in PHPSingleton

Used to replace global variables[changing the name does not change the problem]

Violates the Single Responsibility Principle[creation + singleton class functionality]

NO!

Design pattern in PHPSingleton

private function __construct() {}

Design pattern in PHPSingleton

private static $instance = false;

Design pattern in PHPSingleton

public static function getInstance() { if (false == self::$instance) { self::$instance = new self(); }

return self::$instance;}

Design pattern in PHPSingleton

class Singleton {

private static $instance = false;

private function __construct() {}

public static function getInstance() { if (false == self::$instance) { self::$instance = new self(); }

return self::$instance; }}

$instance = Singleton::getInstance();

Design pattern in PHPFactory method

Design pattern in PHPFactory method

Classes delegate responsibility of building objetsLocalize the knowledge of which class is the delegate

Design pattern in PHPFactory method

PHP most used implementation:Parameterized factory method

Design pattern in PHPFactory method

class Factory {

public function build($condition) {...}

}

Design pattern in PHPFactory method

interface Document { ...}

Design pattern in PHPFactory method

MyDoc implements Document {...}

YourDoc implements Document {...}

TheirDoc implements Document {...}

Design pattern in PHPFactory method

class Factory {

/* @return Document */ public function build($condition) {...}

}

Design pattern in PHPFactory methodclass DocumentReaderFactory {

public function build($type) { switch ($type) { case 'txt': return new TxtReader(); case 'doc': return new DocReader(); //... } }}

foreach ($documents as $document) { $factory = new DocumentReaderFactory(); $reader = $factory->build($document->getType()); $reader->read($document); }

Design pattern in PHPAdapter

Design pattern in PHPAdapter

Converts the interface of a class into another interface

Design pattern in PHPAdapter

An existing class interface does not match what you need

To create a reusable class

Design pattern in PHPAdapter

interface AdapterInterface { ...}

Design pattern in PHPAdapter

by class inheritance

Adapter exteds Adaptee implements AdapterInterface { ...}

Design pattern in PHPAdapter

by objects composition

Adapter implements AdapterInterface { public function __construct(Adaptee $adaptee){ $this->adaptee = $adaptee; }

...}

Design pattern in PHPAdapter

interface FileOperationsInterface {

public function getContent($filename);

public function putContent($filename, $data);

public function removeFile($filename);

}

Design pattern in PHPAdapter

by class inheritance

class FTPFileAdapter extends FTPFileRepository implements FileOperationsInterface {

public function getContent($filename) { … } public function putContent($local_file, $data) { … } public function removeFile($filename) { … }}

Design pattern in PHPAdapter

by objects compositionclass FTPFileAdapter implements FileOperationsInterface {

public function __construct(FTPFileRepository $repository) { $this->repository = $repository; }

public function getContent($filename) { $this->repository->download($local_file, $filename); return file_get_content($local_file); }

public function putContent($local_file, $data) { file_put_contents($local_file, $data); $this->repository->upload($remote_file, $local_file); }

public function removeFile($filename){ $this->repository->remove($filename); }}

Design pattern in PHPTemplate method

Design pattern in PHPTemplate method

Defines the skeleton of an algorithm in an operation, deferring some steps to subclasses

Design pattern in PHPTemplate method

Common behavior localized in a common class

Implements the invariant parts of an algorithm onceLeaves it up to subclasses the behavior that can vary

To control subclasses extensions

Design pattern in PHPTemplate method

Classes implementing a template method should:

specify hooks (may be overridden)

specify abstract operations (must be overridden)

Design pattern in PHPTemplate method

abstract operations (must be overridden)

ie: use prefix “DO”DoRead()DoWrite()

DoSomething()

Design pattern in PHPTemplate method

abstract class Reader {

abstract protected function openFile($filename); abstract protected function readFile(); abstract protected function closeFile();

public function readFileAlgorithm($filename) { $this->openFile($filename); $content = $this->readFile(); $this->closeFile(); return $content }

Design pattern in PHPTemplate method

class XMLReader extends Reader {

protected function openFile($filename) { $this->xml = simplexml_load_file($filename); }

protected function readFile() { return $this->xml->description; } public function closeFile(){}

}

Design pattern in PHPclass CSVReader extends Reader {

protected function openFile($filename) { $this->handle = fopen($filename, "r"); } protected function closeFile() { fclose($this->handle); }

protected function readFile() { $data = fgetcsv($this->handle); return $data[3]; //description }}

Template method

Design pattern in PHP

class Parent { protected function hook() {}

public function doSomething() { //... $this->hook(); }}

Template methodHooks

Design pattern in PHP

class Child extends Parent {

protected function hook() { //My logic to add into the doSomething method }

}

Template methodHooks

Design pattern in PHPDependency Injection

Design pattern in PHPDependency Injection

Components are given their dependencies through their constructors, methods, or directly into fields

Design pattern in PHPDependency Injection

Those components do not get their dependencies themselves, or instantiate them directly

Design pattern in PHPDependency

Injection

class A {

public function doSomething() { $b = new B(); //... }} NO!

Design pattern in PHP

class A { public function construct(B $b) { $this->b = $b; }

//...} YES!

DependencyInjection

Design pattern in PHP

class A { public function setB(B $b) { $this->b = $b; }

//...}

DependencyInjection

YES!

Design pattern in PHP

class A { public $b;

//...}

$a = new A();$a->b = new B();

DependencyInjection

YES!

Design pattern in PHP

class A implements DiInterface{}

interface DiInterface {

public function setB(B $b);

}

DependencyInjection

YES!

Design pattern in PHP

Dependency Injection

Dependency Injection Container&

Inversion of control

ReferencesDesign Patterns: Elements of Reusable Object-Oriented Software

E. Gamma, R. Helm, R. Johnson, J. VlissidesAddison-Wesley 1974

Martin Fowler - http://martinfowler.com/bliki/InversionOfControl.html

PicoContainer Documentation: http://picocontainer.org/injection.html

SourceMaking - Design Patterns: http://sourcemaking.com/design_patterns

PHP best practices - Pattern in PHP: http://www.phpbestpractices.it

Filippo De Santis - fd@ideato.it - @filippodesantis

Thank you!