PHP设计模式之装饰者模式代码实例

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();