学步园

1、作用

为了在实现多态的时候不造成内存泄露,

如果基类析构函数前不加vitual，派生类对象被销毁后，只会调用基类的析构函数，而不会去调用派生类的析构函数。

2、对于正常的函数，如果基类中声明为virtual，则派生类可以不用再写virtual

// CPPTest.cpp : Defines the entry point for the console application.<br /> //<br /> #include "stdafx.h"<br /> class Base<br /> {<br /> public:<br /> Base(){}<br /> virtual ~Base()<br /> {<br /> printf("Base Destructor!/n");<br /> }<br /> virtual void Func()<br /> {<br /> printf("Base Func!/n");<br /> }<br /> private:<br /> int m_iData;<br /> };<br /> class Derived : public Base<br /> {<br /> public:<br /> Derived(){}<br /> ~Derived()<br /> {<br /> printf("Derived Destructor!/n");<br /> }<br /> void Func()<br /> {<br /> printf("Derived Func!/n");<br /> }<br /> };<br /> class Derived2 : public Derived<br /> {<br /> public:<br /> Derived2(){}<br /> ~Derived2()<br /> {<br /> printf("Derived2 Destructor!/n");<br /> }<br /> void Func()<br /> {<br /> printf("Derived2 Func!/n");<br /> }<br /> };</p> <p>int main(int argc, char* argv[])<br /> {<br /> Base *pb = new Base;<br /> pb->Func();<br /> Base *pd = new Derived;<br /> pd->Func();<br /> Base *pd2 = new Derived2;<br /> pd2->Func();<br /> delete pb;<br /> delete pd;<br /> delete pd2;<br /> return 0;<br /> }<br />  

结果：

Base Func!

Derived Func!

Derived2 Func!

Base Destructor!

Derived Destructor!

Base Destructor!

Derived2 Destructor!

Derived Destructor!

Base Destructor!