PHP设计模式之装饰模式

装饰模式：动态地给一个对象添加一些额外的职责，就增加功能来说，装饰模式比生成子类更为灵活

abstract class Component
{
    public abstract function Operation();
}

class ConcreteComponent extends Component
{
    function Operation()
    {
        echo '具体对象的操作
';
    }
}

class Decorator extends Component
{
    protected $component;
    public function SetComponent(Component $component)
    {
        $this->component = $component;
    }

    public function Operation()
    {
        if ($this->component != null){
            $this->component->Operation();
        }
    }
}

class ConcreteDecoratorA extends Decorator
{
    private $addedState;

    function Operation()
    {
        parent::Operation();
        $this->addedState = 'New State';
        echo '具体装饰对象A的操作';
    }
}
class ConcreteDecoratorB extends Decorator
{
    private $addedState;

    function Operation()
    {
        parent::Operation();
        $this->addedBehavior();
        echo '具体装饰对象B的操作';
    }

    private  function addedBehavior()
    {

    }
}

$c = new ConcreteComponent();
$d1 = new ConcreteDecoratorA();
$d2 = new ConcreteDecoratorB();

$d1->SetComponent($c);
$d2->SetComponent($d1);

$d1->Operation();
echo '
';
echo '
';
$d2->Operation();

• 因为装饰模式对象作为子对象的包装，所以保持基类中的方法尽可能少是很重要的。如果一个基类具有大量特性，那么装饰对象不得不为他们包装的对象的所有public方法加上委托。