在实现多态时，当用基类操作派生类，在析构时防止只析构基类而不析构派生类的状况发生。

class Base {

Base(){}

~Base(){cout<<"Base::~Base()"<<endl;}

virtual void Work(){cout<<"Base::Work"<<endl;}

};


class Drive : public Base {

Drive(){}

~Drive(){cout<<"Drive::~Drive()"<<endl;}

virtual void Work(){cout<<"Drive::Work"<<endl;}

};


Base *pBase = new Drive();

pBase->Work();

delete pBase


输出：

Drive::Work

Base::~Base()

对象没有被完全delete。


如果在~Base()之前加上virtual ，输出

Drive::Work

Drive::~Drive()

Base::~Base()