virtual ~ClxDerived()

最新推荐文章于 2019-11-19 17:40:35 发布

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本文通过几个C++示例展示了基类指针指向派生类对象时，使用delete释放内存的过程。重点介绍了虚析构函数的作用及虚函数表在多态中的应用。

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// AnotherDemo.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include "iostream.h"

class ClxBase
{
public:
	ClxBase() {}
	virtual ~ClxBase() { cout << "Output from the destructor of class ClxBase!" << endl; }
	virtual void DoSomething() { cout << "Do something in class ClxBase!" << endl; }
};

class ClxDerived : public ClxBase
{
public:
	ClxDerived() {};
	virtual ~ClxDerived() { cout << "Output from the destructor of class ClxDerived!" << endl; }

	//此处的virtual可以去掉
	virtual void DoSomething() { cout << "Do something in class ClxDerived!" << endl; }
	//此处的virtual可以去掉
};

class ClxThrived : public ClxDerived
{
public:
	ClxThrived(){}
	virtual ~ClxThrived(){cout << "Output from the destructor of class ClxThrived!" << endl;}
	//此处的virtual可以去掉
	virtual void DoSomething(){cout << "Do something in class ClxThrived!" << endl;}
	//此处的virtual可以去掉
};

void main()
{
	cout << "ClxBase *pTest1 = new ClxBase" << endl;
	ClxBase *pTest1 = new ClxBase;
	pTest1->DoSomething();
	delete pTest1;//1

	cout << "ClxBase *pTest2 = new ClxDerived" << endl;
	ClxBase *pTest2 = new ClxDerived;
	pTest2->DoSomething();
	delete pTest2;//2 用基类的指针删除一个派生类的对象时

	cout << "ClxDerived *pTest3 = new ClxDerived" << endl;
	ClxDerived *pTest3 = new ClxDerived;
	pTest3->DoSomething();
	delete pTest3;//3

	cout << "ClxBase *pTest4 = new ClxThrived" << endl;
	ClxBase *pTest4 = new ClxThrived;
	pTest4->DoSomething();
	delete pTest4;//4 用基类的指针删除一个派生类的对象时

	cout << "ClxDerived *pTest5 = new ClxThrived" << endl;
	ClxDerived *pTest5 = new ClxThrived;
	pTest5->DoSomething();
	delete pTest5;//5 用基类的指针删除一个派生类的对象时

	cout << "ClxThrived *pTest6 = new ClxThrived" << endl;
	ClxThrived *pTest6 = new ClxThrived;
	pTest6->DoSomething();
	delete pTest6;//6 
}

/*
ClxBase *pTest1 = new ClxBase
Do something in class ClxBase!
Output from the destructor of class ClxBase!
ClxBase *pTest2 = new ClxDerived
Do something in class ClxDerived!
Output from the destructor of class ClxDerived!
Output from the destructor of class ClxBase!
ClxDerived *pTest3 = new ClxDerived
Do something in class ClxDerived!
Output from the destructor of class ClxDerived!
Output from the destructor of class ClxBase!
ClxBase *pTest4 = new ClxThrived
Do something in class ClxThrived!
Output from the destructor of class ClxThrived!
Output from the destructor of class ClxDerived!
Output from the destructor of class ClxBase!
ClxDerived *pTest5 = new ClxThrived
Do something in class ClxThrived!
Output from the destructor of class ClxThrived!
Output from the destructor of class ClxDerived!
Output from the destructor of class ClxBase!
ClxThrived *pTest6 = new ClxThrived
Do something in class ClxThrived!
Output from the destructor of class ClxThrived!
Output from the destructor of class ClxDerived!
Output from the destructor of class ClxBase!
Press any key to continue
*/