PHP设计模式装饰器与代理模式

PHP设计模式装饰器与代理模式

装饰器模式和代理模式在结构上有点相似，但目的完全不同。装饰器动态添加功能，代理控制访问。今天用代码说明两者的区别。

装饰器模式的核心是层层包装，每个装饰器添加一点功能。

```php
interface Notification
{
public function send(string $message): void;
}

class BasicNotification implements Notification
{
public function send(string $message): void
{
echo "发送消息: $message\n";
}
}

abstract class NotificationDecorator implements Notification
{
protected Notification $notification;

public function __construct(Notification $notification)
{
$this->notification = $notification;
}
}

class EmailDecorator extends NotificationDecorator
{
private string $email;

public function __construct(Notification $notification, string $email)
{
parent::__construct($notification);
$this->email = $email;
}

public function send(string $message): void
{
$this->notification->send($message);
echo "发送邮件至 {$this->email}: $message\n";
}
}

class SmsDecorator extends NotificationDecorator
{
private string $phone;

public function __construct(Notification $notification, string $phone)
{
parent::__construct($notification);
$this->phone = $phone;
}

public function send(string $message): void
{
$this->notification->send($message);
echo "发送短信至 {$this->phone}: $message\n";
}
}

class LogDecorator extends NotificationDecorator
{
public function send(string $message): void
{
echo "[日志] 开始发送\n";
$this->notification->send($message);
echo "[日志] 发送完成\n";
}
}

$notification = new BasicNotification();
$notification = new EmailDecorator($notification, 'user@example.com');
$notification = new SmsDecorator($notification, '13800138000');
$notification = new LogDecorator($notification);

$notification->send('系统更新通知');
?>
>

代理模式在需要控制对象访问时使用。

```php
interface Image
{
public function display(): void;
}

class RealImage implements Image
{
private string $filename;

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

private function loadFromDisk(): void
{
echo "从磁盘加载图片: {$this->filename}\n";
}

public function display(): void
{
echo "显示图片: {$this->filename}\n";
}
}

class ImageProxy implements Image
{
private ?RealImage $realImage = null;
private int $accessCount = 0;

public function __construct(private string $filename) {}

public function display(): void
{
$this->accessCount++;
echo "第{$this->accessCount}次访问\n";

if ($this->realImage === null) {
$this->realImage = new RealImage($this->filename);
}

$this->realImage->display();
}
}

$image = new ImageProxy('photo.jpg');
$image->display();
$image->display();
echo "访问次数: {$image->getAccessCount()}\n";
?>
>

保护代理控制访问权限。

```php
interface Document
{
public function getContent(): string;
}

class SecureDocument implements Document
{
private string $content;

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

public function getContent(): string
{
return $this->content;
}
}

class DocumentProxy implements Document
{
private ?SecureDocument $document = null;
private array $allowedRoles;

public function __construct(string $content, array $allowedRoles)
{
$this->document = new SecureDocument($content);
$this->allowedRoles = $allowedRoles;
}

public function getContent(): string
{
$role = $_SESSION['role'] ?? 'guest';
if (!in_array($role, $this->allowedRoles)) {
throw new RuntimeException("权限不足");
}
return $this->document->getContent();
}
}
?>

装饰器和代理的主要区别是用途不同。装饰器用于增强功能，代理用于控制访问。装饰器接收被装饰对象作为参数，代理则自己创建或引用目标对象。理解了这两种模式的区别，在实际项目中就能根据需求选择合适的方案。