注册模式

目的

在开发应用程序过程中,为了实现对象的集中存储,我们通常会使用只包含静态方法的抽象类(或单例模式)来实现。但这种方式会引入全局变量,我们在任何时候都应该避免这种情况,而应该使用依赖注入来实现。

UML 类图

注册模式类图

代码

Registry.php

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<?php declare(strict_types = 1);

namespace DesignPatterns\Extend\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

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<?php

namespace DesignPatterns\Extend\Registry;

class Service
{

}

测试

Tests/RegistryTest.php

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<?php declare(strict_types = 1);

namespace DesignPatterns\Extend\Registry\Tests;

use InvalidArgumentException;
use DesignPatterns\Extend\Registry\Registry;
use DesignPatterns\Extend\Registry\Service;
use PHPUnit\Framework\MockObject\MockObject;
use PHPUnit\Framework\TestCase;

class RegistryTest extends TestCase
{
/**
* @var Service
*/
private MockObject $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);
}
}