PHP 设计模式实战案例解析

interface Shape {
  public function draw();
}

class Square implements Shape {
  public function draw() {
    echo "Drawing a square.\n";
  }
}

class Circle implements Shape {
  public function draw() {
    echo "Drawing a circle.\n";
  }
}

class ShapeFactory {
  public static function createShape(string $type): Shape {
    switch ($type) {
      case "square":
        return new Square();
      case "circle":
        return new Circle();
      default:
        throw new Exception("Invalid shape type.");
    }
  }
}

// Usage
$factory = new ShapeFactory();
$square = $factory->createShape("square");
$square->draw(); // 输出：Drawing a square.

interface Observer {
  public function update(Subject $subject);
}

class Subject {
  protected $observers = [];

  public function attach(Observer $observer) {
    $this->observers[] = $observer;
  }

  public function detach(Observer $observer) {
    $key = array_search($observer, $this->observers);
    if ($key !== false) {
      unset($this->observers[$key]);
    }
  }

  public function notify() {
    foreach ($this->observers as $observer) {
      $observer->update($this);
    }
  }
}

class Post extends Subject {
  private $title;
  private $body;

  // ... Post related methods

  public function publish() {
    $this->notify();
  }
}

class EmailObserver implements Observer {
  public function update(Subject $subject) {
    // Send an email notification for the new post.
  }
}

class PushObserver implements Observer {
  public function update(Subject $subject) {
    // Send a push notification for the new post.
  }
}

// Usage
$post = new Post();
$observer1 = new EmailObserver();
$observer2 = new PushObserver();
$post->attach($observer1);
$post->attach($observer2);
$post->publish(); // Sends email and push notifications for the new post.