Registry PHP Tasarım Deseni

Uygulama genelinde sıkça kullanılan nesneleri (örn. Yapılandırma (Configuration)) merkezi bir saklama alanında tutma mimarisidir. Bu sıklıkla statik yöntemlere sahip sınıflar (veya Tekilleme (Singleton) deseni) kullanılarak yapılır. Ancak unutmayın, bu genelgeçer bir durum (global state) ortaya koyar ki, bunu her zaman uygulamaktan kaçınmak gerekir. Bunun yerine, gereklilik hallerinde Bağımlılık Aktarımı (Dependency Injection) kullanılmalıdır.

Örneğe ait kodlar;

<?php 
// Registry.php
declare(strict_types=1);

namespace DesignPatterns\Structural\Registry;

use InvalidArgumentException;

abstract class Registry
{
    const LOGGER = 'logger';

    /**
     * this introduces global state in your application which can not be mocked up for testing
     * and is therefor considered an anti-pattern! Use dependency injection instead!
     *
     * @var Service[]
     */
    private static array $services = [];

    private static array $allowedKeys = [
        self::LOGGER,
    ];

    public static function set(string $key, Service $value)
    {
        if (!in_array($key, self::$allowedKeys)) {
            throw new InvalidArgumentException('Invalid key given');
        }

        self::$services[$key] = $value;
    }

    public static function get(string $key): Service
    {
        if (!in_array($key, self::$allowedKeys) || !isset(self::$services[$key])) {
            throw new InvalidArgumentException('Invalid key given');
        }

        return self::$services[$key];
    }
}

// Service.php
namespace DesignPatterns\Structural\Registry;

class Service
{

}

Test İşlemi şu şekilde olacaktır;

// Tests/RegistryTest.php
declare(strict_types=1);

namespace DesignPatterns\Structural\Registry\Tests;

use InvalidArgumentException;
use DesignPatterns\Structural\Registry\Registry;
use DesignPatterns\Structural\Registry\Service;
use PHPUnit\Framework\TestCase;

class RegistryTest extends TestCase
{
    private Service $service;

    protected function setUp(): void
    {
        $this->service = $this->getMockBuilder(Service::class)->getMock();
    }

    public function testSetAndGetLogger()
    {
        Registry::set(Registry::LOGGER, $this->service);

        $this->assertSame($this->service, Registry::get(Registry::LOGGER));
    }

    public function testThrowsExceptionWhenTryingToSetInvalidKey()
    {
        $this->expectException(InvalidArgumentException::class);

        Registry::set('foobar', $this->service);
    }

    /**
     * notice @runInSeparateProcess here: without it, a previous test might have set it already and
     * testing would not be possible. That's why you should implement Dependency Injection where an
     * injected class may easily be replaced by a mockup
     *
     * @runInSeparateProcess
     */
    public function testThrowsExceptionWhenTryingToGetNotSetKey()
    {
        $this->expectException(InvalidArgumentException::class);

        Registry::get(Registry::LOGGER);
    }
}