020--C++养成之路（多态：虚析构）

笔记：虚析构函数（virtual）
没使用virtual:
#include<iostream>
#include<string>
using namespace std;
//虚析构
class A{
public:
  A(){
  cout<<"A构造"<<endl;
  }
  ~A(){
  cout<<"A析构"<<endl;
  }
};
class B:public A{
  int* p;
public:
  B(){
  p=new int(10);
  cout<<"B构造"<<endl;
  }
  ~B(){
    if(p){
    delete p;
    }
    cout<<"B析构"<<endl;
  }
};

int main(){
  A* a=new B();
  delete a;
  getchar();
  return 0;
}

结果：

使用了virtual:
#include<iostream>
#include<string>
using namespace std;
//虚析构
class A{
public:
  A(){
  cout<<"A构造"<<endl;
  }
  virtual ~A(){
  cout<<"A析构"<<endl;
  }
};
class B:public A{
  int* p;
public:
  B(){
  p=new int(10);
  cout<<"B构造"<<endl;
  }
  ~B(){
    if(p){
    delete p;
    }
    cout<<"B析构"<<endl;
  }
};

int main(){
  A* a=new B();
  delete a;
  getchar();
  return 0;
}

结果：