C++,类和对象-多态，计算器的实现

#include 
using namespace  std;
#include

//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;
        } 
        //如果需要扩展新功能，需要修改源代码
        //在真正开发中提倡开闭原则
        //开闭原则：对扩展进行开放，对修改进行关闭

    }

    int m_Num1;//操作数1
    int m_Num2;//操作数2
};

void test01()
{
    //创建计算器对象
    Calculator c;
    c.m_Num1 = 20;
    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
//多态的好处；
//1、组织结构清晰，模块化
//2、可读性强
//3、对于前期和后期的扩展和维护性高

//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 = 100;
    abc->m_Num2 = 20;

    cout << abc->m_Num1 << "+" << abc->m_Num2 << "=" << abc->getResult() << endl;
    //用完后记得销毁,存储在堆区，记得释放
    delete abc;

    //减法运算
    abc = new SubCalculator;
    abc->m_Num1 = 100;
    abc->m_Num2 = 20;

    cout << abc->m_Num1 << "-" << abc->m_Num2 << "=" << abc->getResult() << endl;
    //用完后记得销毁,存储在堆区，记得释放
    delete abc;

    //乘法运算
    abc = new MulCalculator;
    abc->m_Num1 = 100;
    abc->m_Num2 = 20;

    cout << abc->m_Num1 << "*" << abc->m_Num2 << "=" << abc->getResult() << endl;
    //用完后记得销毁,存储在堆区，记得释放
    delete abc;
}

int main()
{
    //test01();
    test02();
}

总结：
//多态的好处；
//1、组织结构清晰，模块化
//2、可读性强
//3、对于前期和后期的扩展和维护性高