设计模式学习2 工厂模式

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<<result<<endl;
}