析构函数、虚析构函数、纯虚函数

#include<iostream>
using namespace std;

class parent
{
public:
    parent()
    {
        cout << "父类构造" << endl;
    }
    ~parent()
    {
        cout << "父类析构" << endl;
    }
};

class child :public parent
{
public:
    child()
    {
        cout << "子类构造" << endl;
    }
    ~child()
    {
        cout << "子类析构" << endl;
    }
};


int main()
{
    {
        parent* A = new child();
        delete A;
    }
    /*父类构造
      子类构造
      父类析构*/
    system("pause");
    return 0;
}

#include<iostream>
  using namespace std;
  class parent
  {
  public:
      parent()
      {
          cout << "父类构造" << endl;
      }
      virtual ~parent()
      {
          cout << "父类析构" << endl;
      }
  };

  class child :public parent
  {
  public:
      child()
      {
          cout << "子类构造" << endl;
      }
      virtual ~child()
      {
          cout << "子类析构" << endl;
      }
  };
  int main()
  {
      {
          parent* A = new child();
          delete A;
      }
    /*父类构造
      子类构造
      子类析构
      父类析构*/
      system("pause");
      return 0;
  }