设计模式（二）：装饰器模式（Decorator）

应用场景

装饰器模式，能有效地把核心职责和附加功能隔离开。比如微信机器人，就和适合用装饰器模式，把核心功能（接收信息等）和其他附件功能（比如自动回复，根据照片识别年龄）隔开。

UML图

装饰器模式.png

代码实现

1. component.php

<?php

//定义职责，给其他的类继承
abstract class Component
{
    public abstract function operation();
}

2. concreteComponent.php

<?php
require_once './Component.php';

/**
 * 对应核心业务
 */
class ConcreteComponent extends Component
{
    public function operation()
    {
        // TODO: Implement operation() method.
        echo '核心业务', PHP_EOL;
    }
}

3. decorator.php

<?php
/**
 * 抽象装饰器类，对应附加业务，用于给具体的装饰器继承
 */
abstract class Decorator extends Component
{
    /**
     * @var Component
     */
    protected $component;

    public function setComponent(Component $component)
    {
        $this->component = $component;
    }

    public function operation()
    {
        // TODO: Implement operation() method.
        if ($this->component != null) {
            $this->component->operation();
        }
    }
}

3. ConcreteDecoratorA.php 和 ConcreteDecoratorB.php

<?php

//具体的装饰器对象
class ConcreteDecoratorA extends Decorator
{
    public function operation()
    {
        parent::operation(); // TODO: Change the autogenerated stub

        echo 'ConcreteDecoratorA 的操作' , PHP_EOL;
    }
}

//具体的装饰器B
class ConcreteDecoratorB extends Decorator
{
    public function operation()
    {
        parent::operation(); // TODO: Change the autogenerated stub
        echo 'ConcreteDecoratorB 的操作' , PHP_EOL;
    }
}

4. 调用以上代码

<?php
require_once './Component.php';
require_once './Decorator.php';
require_once './ConcreteComponent.php';
require_once './ConcreteDecoratorA.php';
require_once './ConcreteDecoratorB.php';

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

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

$d2->operation();

输出结果

输出