c++学习笔记_案例-多态-计算器类（来自哔站黑马程序员-c++教学视频）

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

多态优点：

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

#include<iostream>
using namespace std;

//分别利用普通写法和多台技术实现计算器

//普通写法实现计算器
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，需要修改源码
		//在真实的开发过程中，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;
	int m_Num2;
};

//利用多态实现计算器
//1、组织结构清晰
//2、可读性强
//3、对于前期和后期维护性高

//实现计算器抽象类
class AbstractCalculator
{
public:
	virtual int getResult()
	{
		return 0;
	}

	int m_Num1;
	int m_Num2;
};

class AddCalculator :public AbstractCalculator
{
public:
	int getResult()
	{
		return m_Num1 + m_Num2;
	}
};


class SubCalculator :public AbstractCalculator
{
public:
	int getResult()
	{
		return m_Num1 - m_Num2;
	}
};

class MulCalculator :public AbstractCalculator
{
public:
	int getResult()
	{
		return m_Num1 * m_Num2;
	}
};

void test01()
{
	Calculator c;
	c.m_Num1 = 10;
	c.m_Num2 = 10;
	cout << c.m_Num1 << " + " << c.m_Num2 << " = " << c.getResult("+") << endl;
}

void test02()
{
	//多态使用条件：父类指针或引用  指向  子类对象

	//加法运算
	AbstractCalculator* abc = new AddCalculator;
	abc->m_Num1 = 10;
	abc->m_Num2 = 10;
	cout << abc->m_Num1 << " + " << abc->m_Num2 << " = " << abc->getResult() << endl;
	delete abc;//记得销毁

	//减法指针
	abc = new SubCalculator;
	abc->m_Num1 = 100;
	abc->m_Num2 = 100;
	cout << abc->m_Num1 << " - " << abc->m_Num2 << " = " << abc->getResult() << endl;
	delete abc;//记得销毁

	//减法指针
	abc = new MulCalculator;
	abc->m_Num1 = 100;
	abc->m_Num2 = 100;
	cout << abc->m_Num1 << " - " << abc->m_Num2 << " = " << abc->getResult() << endl;
	delete abc;//记得销毁

}

int main()
{
	test02();
	system("pause");
	return 0;
}