php 工厂方法模式

#使用工厂方法模式是不知道要创建类的对象有哪些.
interface IFactory
{
    public function  CreateOperation();#工厂方法模式只有单个产品

}

class Operation extends Model
{

    private   $numberA;
    private   $numberB;


    public function getResult(){

        $result = 0;

        return $result;

    }

    public  function getNumberA(){

        return $this->numberA;
    }
    public  function  setNumberA($numberA){

        $this->numberA = $numberA;

    }

    public  function getNumberB(){

        return $this->numberB;
    }
    public  function  setNumberB($numberB){

        $this->numberB = $numberB;

    }




}

class OperationAdd extends  Operation
{

    public  function  getResult()
    {
       $result =  0 ;

       $result = $this->numberA + $this->numberB;

       return $result;


    }

}

class OperationSub extends  Operation
{

    public  function  getResult()
    {
       $result = 0;

       $result = $this->numberA - $this->numberB;

       return $result;
    }

}

class OperationMul extends  Operation
{
    public  function getResult(){

        $result = 0;

        $result = $this->numberA  *  $this->numberB;

        return $result;

    }

}

class OperationDiv extends  Operation
{
    public  function  getResult(){

        $result =  0;
        if ($this->numberA == 0){

            throw new HttpException("除数不能为0");
        }

        $result = $this->numberA  /  $this->numberB;

        return $result;
    }

}

class AddFactory implements IFactory
{

    public  function CreateOperation()
    {
        return new OperationAdd();
    }


}

class SubFactory implements IFactory
{

    public  function CreateOperation()
    {
        return new  OperationSub();
    }

}

class MulFactory  implements IFactory
{

    public  function CreateOperation()
    {
      return new OperationMul();
    }

}

class DivFactory  implements IFactory
{

    public  function CreateOperation()
    {
       return new  OperationDiv();
    }

}

$operFactory = new AddFactory();

$oper = $operFactory->CreateOperation();

$oper->numberA  = 1;

$oper->numberB  = 2;

$result = $oper->getResult();

echo $result;

简单工厂和工厂方法的区别:简单工厂模式的最大优点在于工厂类中包含了必要的逻辑判断,根据客户端的选择条件动态实例化相关的类，但是如果要添加新的功能,就要修改里面的case条件修改原有的类，这样违背了开放-封闭原则。工厂方法模式,定义一个用于创建对象的接口,让子类决定实例化
那个类。工厂方法使一个类的实例化延迟到其子类。
工厂方法模式实现时,客户端需要决定实例化那一个工厂来实现运算类，选择判断的问题还是存在的,也就是说,工厂方法把简单工厂的内部逻辑判断移到了客户端代码来进行