C++基础(十九)多态、virtual关键字的使用、虚函数、纯虚函数

没啥好说的上代码 

# include <iostream>
using namespace std;

class Animals 
{
public:
	virtual void sayHello()
	{
		cout << "Animals salHello~" << endl;
	}
};

class Dog :public Animals 
{
public:
	void sayHello()
	{
		cout << "Dog salHello~" << endl;
	}
};

void sayDt(Animals &an) 
{
	an.sayHello();
}

void testDT() 
{
	Dog dd;
	sayDt(dd);
}
int main() 
{
	testDT();
	return 0;
}

---

#include <iostream>
using namespace std;

class Base 
{
public:
	//纯虚函数    拥有纯虚函数的类为抽象类不可实例化
	virtual void sayHello() = 0;
};

class Son :public Base 
{
public:
	virtual void sayHello() 
	{

	};

};

void test09() 
{
	//new Base();  报错
	new Son();
}