1.3. Factory Method

1.3.1. Rôle

The good point over the SimpleFactory is you can subclass it to implement different ways to create objects.

For simple cases, this abstract class could be just an interface.

Ce modèle est un « vrai » patron de conception car il applique le principe d’inversion des dépendances (Dependency Inversion principle) alias « D » dans SOLID (voir principes SOLID).

Cela signifie que FactoryMethod dépend d’abstractions et non de classes concrètes. C’est son principal avantage par rapport à SimpleFactory ou StaticFactory.

1.3.2. Diagramme UML

Alt FactoryMethod UML Diagram

1.3.3. Code

Vous pouvez également trouver ce code sur GitHub

Logger.php

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<?php declare(strict_types=1);

namespace DesignPatterns\Creational\FactoryMethod;

interface Logger
{
    public function log(string $message);
}

StdoutLogger.php

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<?php declare(strict_types=1);

namespace DesignPatterns\Creational\FactoryMethod;

class StdoutLogger implements Logger
{
    public function log(string $message)
    {
        echo $message;
    }
}

FileLogger.php

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<?php declare(strict_types=1);

namespace DesignPatterns\Creational\FactoryMethod;

class FileLogger implements Logger
{
    private string $filePath;

    public function __construct(string $filePath)
    {
        $this->filePath = $filePath;
    }

    public function log(string $message)
    {
        file_put_contents($this->filePath, $message . PHP_EOL, FILE_APPEND);
    }
}

LoggerFactory.php

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<?php declare(strict_types=1);

namespace DesignPatterns\Creational\FactoryMethod;

interface LoggerFactory
{
    public function createLogger(): Logger;
}

StdoutLoggerFactory.php

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<?php declare(strict_types=1);

namespace DesignPatterns\Creational\FactoryMethod;

class StdoutLoggerFactory implements LoggerFactory
{
    public function createLogger(): Logger
    {
        return new StdoutLogger();
    }
}

FileLoggerFactory.php

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<?php declare(strict_types=1);

namespace DesignPatterns\Creational\FactoryMethod;

class FileLoggerFactory implements LoggerFactory
{
    private string $filePath;

    public function __construct(string $filePath)
    {
        $this->filePath = $filePath;
    }

    public function createLogger(): Logger
    {
        return new FileLogger($this->filePath);
    }
}

1.3.4. Test

Tests/FactoryMethodTest.php

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<?php declare(strict_types=1);

namespace DesignPatterns\Creational\FactoryMethod\Tests;

use DesignPatterns\Creational\FactoryMethod\FileLogger;
use DesignPatterns\Creational\FactoryMethod\FileLoggerFactory;
use DesignPatterns\Creational\FactoryMethod\StdoutLogger;
use DesignPatterns\Creational\FactoryMethod\StdoutLoggerFactory;
use PHPUnit\Framework\TestCase;

class FactoryMethodTest extends TestCase
{
    public function testCanCreateStdoutLogging()
    {
        $loggerFactory = new StdoutLoggerFactory();
        $logger = $loggerFactory->createLogger();

        $this->assertInstanceOf(StdoutLogger::class, $logger);
    }

    public function testCanCreateFileLogging()
    {
        $loggerFactory = new FileLoggerFactory(sys_get_temp_dir());
        $logger = $loggerFactory->createLogger();

        $this->assertInstanceOf(FileLogger::class, $logger);
    }
}