案例描述：

分别利用普通写法和多态技术，设计实现两个操作数进行运算的计算器类

多态的优点：

1.代码组织结构清晰
1.可读性强
1.利于前期和后期的扩展以及维护

代码示例：

#include <iostream>
using namespace std;
#include<string>
//分别利用普通写法和多态·技术实现计算器
//普通写法
class Calculator
{
    
    
public:
       int getResult(string oper)
       {
    
    
              if (oper == "+")
              {
    
    
                     return m_Num1 + m_Num2;
              }
              else if (oper == "-")
              {
    
    
                     return m_Num1 - m_Num2;
              }
              else if (oper == "*")
              {
    
    
                     return m_Num1 * m_Num2;
              }
              //如果想扩展新的功能，需求修改源码
              //在真实开发中 提倡 开闭原则
              //开闭原则：对扩展进行开发，对修改进行关闭
       }
       int m_Num1;   //操作数1
       int m_Num2;   //操作数2
};
void test01()
{
    
    
       //差UN构件计算其对象
       Calculator c;
       c.m_Num1 = 10;
       c.m_Num2 = 10;
       cout << c.m_Num1 << "+" << c.m_Num2 << "=" << c.getResult("+") << endl;
       cout << c.m_Num1 << "-" << c.m_Num2 << "=" << c.getResult("-") << endl;
       cout << c.m_Num1 << "*" << c.m_Num2 << "=" << c.getResult("*") << endl;
       
}
//利用多态实现计算器
//使用多态好处
// 1.代码组织结构清晰
//
//2.可读性强
//
//3.利于前期和后期的扩展以及维护
//实现计算器抽象类
class  AbstractCalculator
{
    
    
public:
       virtual int getResult()
       {
    
    
              return 0;
       }
       int m_Num1;
       int m_Num2;
};
//加法计算器类
class AddCalculator :public AbstractCalculator
{
    
    
public:
        int getResult()
       {
    
    
              return m_Num1+m_Num2;
       }
};
//减法计算器类
class SubCalculator :public AbstractCalculator
{
    
    
public:
       int getResult()
       {
    
    
              return m_Num1 - m_Num2;
       }
};
//乘法计算器类
class MulCalculator :public AbstractCalculator
{
    
    
public:
       int getResult()
       {
    
    
              return m_Num1 * m_Num2;
       }
};
void test02()
{
    
    
       //多态使用条件
       //父类指针或者引用指向子类对象
       //加法运算
       AbstractCalculator*abc = new AddCalculator;
       abc->m_Num1 = 13;
       abc->m_Num2 = 10;
       cout << abc->m_Num1 << "+" << abc->m_Num2 << "=" << abc->getResult() <<  endl;
       //用完记得销毁
       delete abc;
       //减法运算
       abc = new SubCalculator;
       abc->m_Num1 = 13;
       abc->m_Num2 = 10;
       cout << abc->m_Num1 << "-" << abc->m_Num2 << "=" << abc->getResult() <<  endl;
       delete abc;
       //乘法运算
       abc = new MulCalculator;
       abc->m_Num1 = 13;
       abc->m_Num2 = 10;
       cout << abc->m_Num1 << "*" << abc->m_Num2 << "=" << abc->getResult() <<  endl;
       delete abc;
}
int main()
{
    
    
       //test01();
       test02();
       return 0;
}

总结：C++开发提倡利用多态设计程序架构，因为多态优点很多

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