虚函数和虚析构函数

代码-A

/*
#include<iostream>//无虚函数
#include<string>
using namespace std;
class Zhu
{
public:
	Zhu(string a, int b, float c) :name(a), age(b), score(c) {}
	void display();
	~Zhu();
protected:float score;
		  string name;
		  int age;
};
Zhu::~Zhu()
{
	cout << "析构函数到此一游" << endl; cin.get();
}
void Zhu::display()
{
	cout << "name:" << name << endl << "age:" << age << endl
		<< "score:" << score << endl;
}
class Jia :public Zhu
{
public:
	Jia(string a, int b, float c, string d, int e) :Zhu(a, b, c), minname(d), agoage(e) {}
	void display();
	~Jia();
private:
	string minname;
	int agoage;		 
};
void Jia::display()
{
	cout << "name:"<<name << endl <<"age:"<<age << endl 
		<< "score:" <<score<< endl <<"minname:"<<minname<< endl
		<< "agoage:" <<agoage<< endl;
}
Jia::~Jia()
{
	cout << "来了又来" << endl;
}
int main()
{
	Zhu first("张三", 19, 99.9);	
	Jia second("奥特曼", 9999, 100, "打怪兽", 7);
	Zhu *p = &first;
	p->display();
	cout << endl;
	p = &second;    //自动进行指针类型转换,将派生类的对象的指针先转换为基类的指针,
	p->display();   //基类指针指向的就是派生类的基类部分
	return 0;
}
*/


/*
#include<iostream>//有虚函数
#include<string>
using namespace std;
class Zhu
{
public:
	Zhu(string a, int b, float c) :name(a), age(b), score(c) {}
	virtual void display();
	~Zhu();
protected:float score;
		  string name;
		  int age;
};
Zhu::~Zhu()
{
	cout << "析构函数到此一游" << endl; cin.get();
}
void Zhu::display()
{
	cout << "name:" << name << endl << "age:" << age << endl
		<< "score:" << score << endl;
}
class Jia :public Zhu
{
public:
	Jia(string a, int b, float c, string d, int e) :Zhu(a, b, c), minname(d), agoage(e) {}
	void display();
	~Jia();
private:
	string minname;
	int agoage;
};
void Jia::display()
{
	cout << "name:" << name << endl << "age:" << age << endl
		<< "score:" << score << endl << "minname:" << minname << endl
		<< "agoage:" << agoage << endl;
}
Jia::~Jia()
{
	cout << "来了又来" << endl;
}
int main()
{
	Zhu first("张三", 19, 99.9);
	Jia second("奥特曼", 9999, 100, "打怪兽", 7);
	Zhu *p = &first;
	p->display();
	cout << endl;
	p = &second;    //虚函数打破了无法通过基类指针去调用派生类对象中的成员函数
	p->display();   //的限制，此时派生类同名成员函数取代了基类的中的虚函数
	return 0;
}
*/

/*
#include<iostream>
using namespace std;
class Zhu{
public:Zhu() {}
	   ~Zhu() { cout << "我是基类的析构函数" << endl; cin.get(); }
};
class Jia:public Zhu {
public:Jia() {}
	   ~Jia() { cout << "我是派生类的析构函数" << endl; }
};
int main()
{
	Zhu *p = new Jia();//用Jia类构造函数初始化Zhu类的,并用new开辟动态存储空间
	delete p;//释放动态存储空间
	return 0;    //只有基类析构函数被调用，不执行派生类析构函数   
}
*/

#include<iostream>
using namespace std;
class Zhu {
public:Zhu() {}
	   virtual~Zhu() //虚析构函数，该类所派生的所有派生类的析构函数也都自动成为虚析构函数
	   { cout << "我是基类的析构函数" << endl; cin.get(); }
};
class Jia :public Zhu {
public:Jia() {}
	   ~Jia() { cout << "我是派生类的析构函数" << endl; }
};
int main()
{
	Zhu *p = new Jia();//用Jia类构造函数初始化Zhu类的,并用new开辟动态存储空间
	delete p;//释放动态存储空间，用了指向派生类对象的基类指针，系统会调用派生类的析构函数
	return 0;    //基类和派生类析构函数都被调用  
}

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