详解 C++ virtual 析构函数

详解 C++ virtual 析构函数

http://blog.csdn.net/lwbeyond/article/details/7497294

第一种情况：基类指针指向派生类对象。

#include <iostream>
using namespace std;

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

class Derived:public Base{
  public:
    ~Derived() {cout<<"~D"<<endl;}
};

int main (){
  Base *b = new Derived; //注意这里
  delete b;
}

这里只有基类(Base)会被析构掉，派生类(Derived)没有被析构。

第二种情况：派生类指针指向派生类对象。

#include <iostream>
using namespace std;

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

class Derived:public Base{
  public:
    ~Derived() {cout<<"~D"<<endl;}
};

int main (){
  Derived *d = new Derived; //注意这里
  delete d;
}

这次基类和派生类都能被析构掉。

第三种情况：基类指针指向派生类对象，但析构函数是virtual 的。

class Base{
public:
  virtual ~Base(){cout<<"~B"<<endl;};
}

class Derived:public Base{
public:
  virtual ~Derived(){cout<<"~D"<<endl;};
}

void main (){
  Base *b=new Derived();
  delete b;
}

这时，基类和派生类对象都能被析构掉。