定义：
装饰者模式就是不修改原类代码和继承的情况下动态扩展类的功能。传统的编程模式都是子类继承父类实现方法重载，使用装饰器模式，只需添加一个新的装饰器对象，更加灵活，避免类数量和层次过多。
角色：
Component（被装饰对象基类）
ConcreteComponent（具体被装饰对象）
Decorator（装饰者基类）
ContreteDecorator（具体的装饰者类）
示例代码：
//被装饰者基类 interface Component { public function operation(); } //装饰者基类 abstract class Decorator implements Component { protected $component; public function __construct(Component $component) { $this->component = $component; } public function operation() { $this->component->operation(); } } //具体装饰者类 class ConcreteComponent implements Component { public function operation() { echo 'do operation'.PHP_EOL; } } //具体装饰类A class ConcreteDecoratorA extends Decorator { public function __construct(Component $component) { parent::__construct($component); } public function operation() { parent::operation(); $this->addedOperationA(); // 新增加的操作 } public function addedOperationA() { echo 'Add Operation A '.PHP_EOL; } } //具体装饰类B class ConcreteDecoratorB extends Decorator { public function __construct(Component $component) { parent::__construct($component); } public function operation() { parent::operation(); $this->addedOperationB(); } public function addedOperationB() { echo 'Add Operation B '.PHP_EOL; } } class Client { public static function main() { /* do operation Add Operation A */ $decoratorA = new ConcreteDecoratorA(new ConcreteComponent()); $decoratorA->operation(); /* do operation Add Operation A Add Operation B */ $decoratorB = new ConcreteDecoratorB($decoratorA); $decoratorB->operation(); } } Client::main();
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