设计模式4.2-工厂模式之工厂方法

<?php
/*
*
* 工厂方法：定义一个创建对象的接口，由子类决定实例化哪个类，把实例化类的逻辑推迟到子类中
*
* 在本示例中：我们在CakeStore的抽象类中定义了创建Cake的接口createCake,子类在继承此抽象类后必须实现此方法，因此，决定实例化哪个类的逻辑推迟到了子类，由子类决定。
*
* 在我们的orderCake方法中，使用了$cake->bake()等方法，而这些方法是由Cake抽象定义的，所以CakeStore依赖于Cake.而具体的Cake对象也依赖于抽象Cake.这种方式避免了我们的CakeStore依赖于具体的Cake类，所以这是依赖倒置原则的很好示例。
*
*/

//抽象蛋糕店
abstract class CakeStore
{
    public function orderCake()
    {
        $cake = $this->createCake();

        $cake->bake();
        $cake->package();
    }

    abstract function createCake();
}

//抽象蛋糕
abstract class Cake
{
    abstract public function bake();

    abstract public function package();
}

//具体蛋糕类
class BeiJingCake extends Cake
{
    public function bake()
    {
        echo "BeiJing cake is baking<br>\n";
    }

    public function package()
    {
        echo "BeiJing cake is packaging<br>\n";
    }
}

class ShangHaiCake extends Cake
{
    public function bake()
    {
        echo "Shang Hai cake is baking<br>\n";
    }

    public function package()
    {
        echo "Shang Hai cake is packaging<br>\n";
    }
}

//具体蛋糕店类
class BeiJingCakeStore extends CakeStore
{
    public function createCake()
    {
        return new BeiJingCake();
    }
}


class ShangHaiCakeStore extends CakeStore
{
    public function createCake()
    {
        return new ShangHaiCake();
    }
}


class Test
{
    public function run()
    {
        $beijingStore = new BeiJingCakeStore();
        $shanghaiStore = new ShangHaiCakeStore();

        $beijingStore->orderCake();
        $shanghaiStore->orderCake();
    }
}

$test = new Test();
$test->run();