每个软件工程师都应该知道的 5 大设计模式

PHP 非常适合实现设计模式，尤其是其现代特性，如属性、枚举和只读属性。以下是每个软件工程师都应该知道的五种基本模式。

1.单例模式

**确保一个类只有一个实例。**

final class Config 
{
    private static ?Config $instance = null;

    private function __construct(public readonly array $settings) {}

    public static function getInstance(): Config 
    {
        return self::$instance ??= new Config(['env' => 'production']);
    }
}

// Usage
$config = Config::getInstance();
echo $config->settings['env']; // Output: production

2.工厂模式

**集中对象创建逻辑。**

class DatabaseFactory 
{
    public static function create(string $type): Database 
    {
        return match ($type) {
            'mysql' => new MySQLDatabase(),
            'postgres' => new PostgresDatabase(),
            default => throw new InvalidArgumentException("Unknown database type"),
        };
    }
}

interface Database { public function connect(): void; }
class MySQLDatabase implements Database { public function connect() { echo "MySQL connected"; } }
class PostgresDatabase implements Database { public function connect() { echo "Postgres connected"; } }

// Usage
$db = DatabaseFactory::create('mysql');
$db->connect(); // Output: MySQL connected

3.观察者模式

**通知多个对象有关状态改变的信息。**

class Event 
{
    private array $listeners = [];

    public function attach(callable $listener): void { $this->listeners[] = $listener; }
    public function trigger(string $data): void { foreach ($this->listeners as $listener) $listener($data); }
}

// Usage
$event = new Event();
$event->attach(fn($data) => print "Listener 1: $data\n");
$event->attach(fn($data) => print "Listener 2: $data\n");

$event->trigger("Event triggered"); 
// Output:
// Listener 1: Event triggered
// Listener 2: Event triggered

4.装饰者模式

**动态地向对象添加行为。**

interface Text { public function render(): string; }

class PlainText implements Text 
{
    public function __construct(private string $text) {}
    public function render(): string { return $this->text; }
}

class BoldText implements Text 
{
    public function __construct(private Text $text) {}
    public function render(): string { return "" . $this->text->render() . ""; }
}

// Usage
$text = new BoldText(new PlainText("Hello, World!"));
echo $text->render(); // Output: Hello, World!

5.策略模式

**在运行时在算法之间切换。**

interface PaymentStrategy { public function pay(float $amount): void; }

class CreditCardPayment implements PaymentStrategy 
{
    public function pay(float $amount): void { echo "Paid $amount with Credit Card\n"; }
}

class PayPalPayment implements PaymentStrategy 
{
    public function pay(float $amount): void { echo "Paid $amount via PayPal\n"; }
}

class PaymentProcessor 
{
    public function __construct(private PaymentStrategy $strategy) {}

    public function execute(float $amount): void 
    {
        $this->strategy->pay($amount);
    }
}

// Usage
$processor = new PaymentProcessor(new PayPalPayment());
$processor->execute(100.00); // Output: Paid 100 via PayPal

这些模式解决了现实世界的问题并且是编写可维护和可扩展的应用程序的基础。

哪种图案与你当前的项目产生共鸣？让我们在评论中讨论吧！🚀