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深入探討C++父類子類中虛函數(shù)的應(yīng)用

更新時(shí)間：2013年05月28日 12:07:32 作者：

本篇文章是對C++父類子類中虛函數(shù)的使用進(jìn)行了詳細(xì)的分析介紹，需要的朋友參考下

構(gòu)造函數(shù)不能是虛函數(shù)，因?yàn)樵谡{(diào)用構(gòu)造函數(shù)創(chuàng)建對象時(shí)，構(gòu)造函數(shù)必須是確定的，所以構(gòu)造函數(shù)不能是虛函數(shù)。
析構(gòu)函數(shù)可以是虛函數(shù)。

1.父類Father.h：

復(fù)制代碼代碼如下:

#pragma once
class Father
{
public:
 Father(void);
 virtual ~Father(void);
 virtual int getCount();
public:
 int count;
};

Father.cpp

復(fù)制代碼代碼如下:

#include "StdAfx.h"
#include "Father.h"
#include <iostream>
using namespace std;
Father::Father(void)
{
 count = 1;
 cout<<"Father is called. count = "<<count<<endl;
}
Father::~Father(void)
{
 cout<<"~Father is called."<<endl;
}
int Father::getCount()
{
 cout<<"Father::getCount() count = "<<count<<endl;
 return count;
}

2.子類Child.h：

復(fù)制代碼代碼如下:

#pragma once
#include "father.h"
class Child :
 public Father
{
public:
 Child(void);
 virtual ~Child(void);
 virtual int getCount();
 int getAge();
public:
 int age;
};

Child.cpp

復(fù)制代碼代碼如下:

#include "StdAfx.h"
#include "Child.h"
#include <iostream>
using namespace std;
Child::Child(void)
{
 count = 2;
 age = 20;
 cout<<"Child is called. count = "<<count<<", age = "<<age<<endl;
}
Child::~Child(void)
{
 cout<<"~Child is called."<<endl;
}
int Child::getCount()
{
 cout<<"Child::getCount() count = "<<count<<endl;
 return count;
}
int Child::getAge()
{
 cout<<"Child::getAge() age = "<<age<<endl;
 return age;
}

3.測試類Test.cpp

復(fù)制代碼代碼如下:

#include "stdafx.h"
#include  <cstdlib>
#include <iostream>
#include "Child.h"
using namespace std;
int _tmain(int argc, _TCHAR* argv[])
{
 Father *father1 = new Father();
 cout<<"father1 count = "<<father1->getCount()<<endl;
 delete father1;
 cout<<"************** father1 end *****************"<<endl<<endl;
 Father *father2 = new Child();
 cout<<"father2 count = "<<father2->getCount()<<endl; // father2 don't have getAge() method
 delete father2;
 cout<<"************** father2 end *****************"<<endl<<endl;
 Child *child = new Child();
 cout<<"child count = "<<child->getCount()<<endl;
 cout<<"child age = "<<child->getAge()<<endl;
 delete child;
 cout<<"************** child end *****************"<<endl<<endl;
 getchar();
 return 0;
}

4.輸出結(jié)果：
Father is called. count = 1
Father::getCount() count = 1
father1 count = 1
~Father is called.
************** father1 end *****************

Father is called. count = 1
Child is called. count = 2, age = 20
Child::getCount() count = 2
father2 count = 2
~Child is called.
~Father is called.
************** father2 end *****************

Father is called. count = 1
Child is called. count = 2, age = 20
Child::getCount() count = 2
child count = 2
Child::getAge() age = 20
child age = 20
~Child is called.
~Father is called.
************** child end *****************

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