7.1 多态案例

 一、案例1：计算器类

1.1 普通方式实现

#include <iostream>
#include <string>
using namespace std;class Calculator
{
public:int num1;int num2;int result(string oper){if (oper == "+")return num1 + num2;else if (oper == "-")return num1 - num2;else if (oper == "*")return num1 * num2;}
};void test1()
{Calculator c;c.num1 = 10;c.num2 = 10;//加法cout << c.num1 << "+" << c.num2 << "=" << c.result("+") << endl;//减法cout << c.num1 << "-" << c.num2 << "=" << c.result("-") << endl;//乘法cout << c.num1 << "*" << c.num2 << "=" << c.result("*") << endl;
}

1.2 多态实现

1.多态实现相对与普通方法代码量更大；

2.但若要增加程序功能（如除法）或出现异常时，普通实现方法需要对result()进行修改；

3.而多态实现方法则将加减分成不同的类，增加新功能不会影响到加减函数，并且某一功能     出现异常时可快速定位，增强代码维护性；

//多态实现
class Abstract_Calculator
{
public:int num1;int num2;virtual int result(){return 0;}
};class Add_Calculator : public Abstract_Calculator
{
public:int result(){return num1 + num2;}
};class Sub_Calculator : public Abstract_Calculator
{
public:int result(){return num1 - num2;}
};void test2()
{cout << "***************多态实现*****************" << endl;Abstract_Calculator* abc = new Add_Calculator;abc->num1 = 10;abc->num2 = 10;cout << abc->num1 << "+" << abc->num2 << "=" << abc->result() << endl;delete abc;abc = new Sub_Calculator;abc->num1 = 10;abc->num2 = 10;cout << abc->num1 << "-" << abc->num2 << "=" << abc->result() << endl;delete abc;
}

 二、案例2：制作饮品

#include <iostream>
#include <string>
using namespace std;class Abstract_Drinking
{
public://1.煮水virtual void zhushui() = 0;//2.冲泡virtual void chongpao() = 0;//3.倒入杯中virtual void daoru() = 0;//4.加...virtual void dao() = 0;//5.总体制作流程void made_progress(){zhushui();chongpao();daoru();dao();}
};class Coffee : public Abstract_Drinking
{
public:void zhushui(){cout << "煮水" << endl;}void chongpao(){cout << "冲泡咖啡" << endl;}void daoru(){cout << "倒入杯中" << endl;}void dao(){cout << "加糖和牛奶" << endl;}
};class Tea : public Abstract_Drinking
{
public:void zhushui(){cout << "煮水" << endl;}void chongpao(){cout << "冲泡茶叶" << endl;}void daoru(){cout << "倒入杯中" << endl;}void dao(){cout << "加柠檬" << endl;}
};void doWork(Abstract_Drinking* abc)
{abc->made_progress();delete abc;
}void test1()
{doWork(new Coffee);cout << "---------------------" << endl;doWork(new Tea);
}int main()
{test1();return 0;
}

三、案例3：电脑组装

#include <iostream>
#include <string>
using namespace std;//CPU抽象类
class CPU
{
public:virtual void calculate() = 0;
};
//显卡抽象类
class VideoCard
{
public:virtual void display() = 0;
};
//内存条抽象类
class Memory
{
public:virtual void storage() = 0;
};
//电脑类
class Computer
{
public:Computer(CPU* cpu, VideoCard* vc, Memory* mem){_cpu = cpu;_vc = vc;_mem = mem;}void DoWork(){_cpu->calculate();_vc->display();_mem->storage();}~Computer(){if (_cpu != NULL){delete _cpu;_cpu = NULL;}if (_vc != NULL){delete _vc;_vc = NULL;}if (_mem != NULL){delete _mem;_mem = NULL;}}
private:CPU* _cpu;VideoCard* _vc;Memory* _mem;
};
//Intel厂商
class IntelCPU: public CPU
{
public:void calculate(){cout << "IntelCPU开始计算了" << endl;}
};
class IntelVideoCard : public VideoCard
{
public:void display(){cout << "IntelVideoCard开始显示了" << endl;}
};
class IntelMemory : public Memory
{
public:void storage(){cout << "IntelMemory开始存储了" << endl;}
};
//Lenovo厂商
class LenovoCPU : public CPU
{
public:void calculate(){cout << "LenovoCPU开始计算了" << endl;}
};
class LenovoVideoCard : public VideoCard
{
public:void display(){cout << "LenovoVideoCard开始显示了" << endl;}
};
class LenovoMemory : public Memory
{
public:void storage(){cout << "LenovoMemory开始存储了" << endl;}
};
//测试
void test1()
{cout << "创建第一台电脑--------------------" << endl;CPU* intel_CPU = new IntelCPU;VideoCard* intel_VideoCard = new IntelVideoCard;Memory* intel_Memory = new IntelMemory;Computer* computer1 = new Computer(intel_CPU, intel_VideoCard, intel_Memory);computer1->DoWork();delete computer1;cout << "创建第二台电脑--------------------" << endl;Computer* computer2 = new Computer(new LenovoCPU, new LenovoVideoCard, new LenovoMemory);computer2->DoWork();delete computer2;
}
int main()
{test1();return 0;
}