c++多态

1.多态案例-计算机实现

class AbstractCalculate
{
public:
	virtual int getResult()
	{
		return 0;
	}

	int num1;
	int num2;
};

//加法
class AddCalculate : public AbstractCalculate
{
	int getResult()
	{
		return num1 + num2;
	}
};

//减法
class SubCalculate : public AbstractCalculate
{
	int getResult()
	{
		return num1 - num2;
	}
};

//乘法
class MulCalculate : public AbstractCalculate
{
	int getResult()
	{
		return num1 * num2;
	}
};

void test01()
{
	//加法运算
	AbstractCalculate* add = new AddCalculate;
	add->num1 = 10;
	add->num2 = 20;

	cout << add->num1 << "+" << add->num2 << "=" << add->getResult() << endl;
	
	//用完后需要销毁
	delete add;

	//减法运算
	AbstractCalculate* sub = new SubCalculate;
	sub->num1 = 20;
	sub->num2 = 10;

	cout << sub->num1 << "-" << sub->num2 << "=" << sub->getResult() << endl;
	delete sub;

	//乘法运算
	AbstractCalculate* mul = new MulCalculate;
	mul->num1 = 10;
	mul->num2 = 20;

	cout << mul->num1 << "*" << mul->num2 << "=" << mul->getResult() << endl;
	delete mul;
}

2.纯虚函数和抽象类

纯虚函数
（使用virtual为虚函数，没有实现的虚函数是纯虚函数 virtual void func() = 0;）
只要有一个纯虚函数，这个类称为抽象类
抽象类特点：
1.无法实例化对象
2.抽象类的子类 必须要重写父类中的纯虚函数，否则也属于抽象类

class Base
{
public:

	virtual void func() = 0;
};

class Son : public Base
{
public:
	virtual void func()
	{
		cout << "func函数调用" << endl;
	}
};

void test01()
{
	//Base b;	//抽象类无法实例化对象

	//Son s = new Son;	//子类必须重写父类中的纯虚函数，否则无法实例化对象
	Base* base = new Son;
	base->func();
}

多态案例-制作饮品

class AbstractDrinking
{
public:
	//煮水
	virtual void Boil() = 0;

	//冲水
	virtual void Brew() = 0;

	//倒入杯中
	virtual void PourInCup() = 0;

	//加入辅料
	virtual void PutSomething() = 0;

	//制作饮品
	void makeDrink()
	{
		Boil();
		Brew();
		PourInCup();
		PutSomething();
	}
};

//制作咖啡
class Coffee : public AbstractDrinking
{
public:
	virtual void Boil()
	{
		cout << "煮水" << endl;
	}

	virtual void Brew()
	{
		cout << "冲泡咖啡" << endl;
	}

	virtual void PourInCup()
	{
		cout << "倒入咖啡杯中" << endl;
	}

	virtual void PutSomething()
	{
		cout << "加入牛奶和糖" << endl;
	}
};

//制作茶叶
class Tea : public AbstractDrinking
{
public:
	virtual void Boil()
	{
		cout << "煮纯净水" << endl;
	}

	virtual void Brew()
	{
		cout << "泡茶叶" << endl;
	}

	virtual void PourInCup()
	{
		cout << "倒入茶杯中" << endl;
	}

	virtual void PutSomething()
	{
		cout << "加入柠檬" << endl;
	}
};

//制作函数
void doWork(AbstractDrinking* abs)
{
	abs->makeDrink();
	delete abs;
}

3.多态案例-组装电脑

class CPU
{
public:
	virtual void calculate() = 0;
};

class VideoCard
{
public:
	virtual void display() = 0;
};

class Memory
{
public:
	virtual void storage() = 0;
};

class Computer
{
public:
	Computer(CPU *cpu,VideoCard *vc, Memory *mem)
	{
		m_cpu = cpu;
		m_vc = vc;
		m_mem = mem;
	}

	~Computer()
	{
		if (m_cpu != NULL)
		{
			delete m_cpu;
			m_cpu = NULL;
		}
		if (m_vc != NULL)
		{
			delete m_vc;
			m_vc = NULL;
		}
		if (m_mem != NULL)
		{
			delete m_mem;
			m_mem = NULL;
		}
	}
	void doWork()
	{
		m_cpu->calculate();
		m_vc->display();
		m_mem->storage();
	}
private:
	CPU* m_cpu;
	VideoCard* m_vc;
	Memory* m_mem;
};

//具体厂商
//Intel厂商
class IntelCPU :public CPU
{
public:
	virtual void calculate()
	{
		cout << "Intel的CPU开始计算了！" << endl;
	}
};

class IntelVideoCard :public VideoCard
{
public:
	virtual void display()
	{
		cout << "Intel的显卡开始显示了！" << endl;
	}
};

class IntelMemory :public Memory
{
public:
	virtual void storage()
	{
		cout << "Intel的内存开始存储了！" << endl;
	}
};

void test01()
{
	//第一台电脑零件
	CPU* intelCpu = new IntelCPU;
	VideoCard* intelVideoCard = new IntelVideoCard;
	Memory* intelMemory = new IntelMemory;

	Computer *computer = new Computer(intelCpu, intelVideoCard, intelMemory);
	computer->doWork();
	delete computer;
}