01 大话设计模式C++实现之简单工厂模式_c++用多态性实现简单工厂模式-优快云博客

本文链接：https://blog.youkuaiyun.com/Woosual/article/details/103516356

本文详细介绍了使用C++实现一个简单计算器的过程，包括运算符封装、异常处理机制以及工厂模式的应用。通过具体代码示例，展示了如何创建加、减、乘、除等基本运算，并在除法中加入对除数为零的异常处理。

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#define _CRT_SECURE_NO_WARNINGS

#include<iostream>
#include<stdexcept>

using namespace std;
//业务的封装过程让业务逻辑与界面逻辑分开，从而使程序容易修改、易于复用
//通过类的封装、继承、多态将程序的耦合度降低

//Operation运算类
class Operation
{
private:
double number_A = 0;
double number_B = 0;
public:

   Operation() {}
   Operation(double a, double b)
   {
       number_A = a;
       number_B = b;
   }
   double getNumberA()
   {
       return number_A;
   }
   void setNumberA(double a)
   {
       number_A = a;
   }
   double getNumberB()
   {
       return number_B;
   }
   void setNumberB(double b)
   {
       number_B = b;
   }
   //利用多态性实现业务
   virtual double getResult()
   {
       double result = 0;
       return result;
   }
};

//加减乘除类
class Add :public Operation
{
public:
   virtual double getResult()
   {
       return getNumberA() + getNumberB();
   }
};

class Sub :public Operation
{
public:
   virtual double getResult()
   {
       return getNumberA() - getNumberB();
   }
};

class Mul :public Operation
{
public:
   virtual double getResult()
   {
       return getNumberA() * getNumberB();
   }
};
class Dev :public Operation
{
public:
   virtual double getResult()
   {
       if (getNumberB() == 0)
       {
           throw overflow_error("除数为零！！！");
       }
       return getNumberA() / getNumberB();
   }
};

//工厂类的实现，依赖于运算类

class OperationFactory
{
public:
   static Operation* createOperatecreate(char operate)
   {
       //c++不支持对字符串进行switch case操作
       Operation *oper = NULL;
       switch (operate)
       {
       case '+':
           oper = new Add;
           break;
       case '-':
           oper = new Sub;
           break;
       case '*':
           oper = new Mul;
           break;
       case '/':
           oper = new Dev;
       default:
           break;
       }
       return oper;
   }

};

void test(double a, char op, double b)
{
   Operation *oper;
   oper = OperationFactory::createOperatecreate(op);
   oper->setNumberA(a);
   oper->setNumberB(b);
   cout << oper->getResult() << endl;
}

int main()
{
   try
   {
       test(10.1, '/', 0);
   }
   catch (overflow_error &e)
   {
       cout << e.what() << endl;
   }

   system("pause");
   return EXIT_SUCCESS;
}