工厂模式其实就是简单模式的升级版本，

 

简单模式将界面与业务逻辑区分开，但是如果不停的增加计算器的运算方式，简单模式中的工厂Factory 中判断的业务逻辑会变非常复杂，这不符合封装的原则。

 

所以在此之上将Factory抽象了出来，代码如下：

 

class Cal{public:   virtual double getResult()   {      return 0;   }   void setPara(double paraA,double paraB)   {      parameterA = paraA;      parameterB = paraB;   }protected:   double parameterA;   double parameterB;};class Plus:public Cal{public:   Plus(){}   double getResult()   {      return parameterA + parameterB;   }};class Minus:public Cal{public:   Minus(){}   double getResult()   {      return parameterA - parameterB;   }};class FactoryInterface{public:   virtual Cal * createCal() = 0;};class AddFactory:public FactoryInterface{public:   Cal *createCal()   {      return new Plus();   }};class MinusFactory:public FactoryInterface{public:   Cal *createCal()   {      return new Minus();   }};void main(){   double paraA = 5,paraB=43,result = 0;   FactoryInterface *factory = new AddFactory;   Cal *cal = factory->createCal();   cal->setPara(paraA,paraB);   result = cal->getResult();   cout<
     
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