多态

---

动态多态

与继承中限定让父类参与但可以带入子类的方法一致
地址软绑定，由输入的决定

class father
{
  public:
  virtual void speak()
  {
    cout<<"father!";
  }
};
class son:public father
{
  public:
  void speak()
  {
    cout<<"son!";
  }
};
void spk(father &f)
{
  f.speak();
}
int main()
{
  son s;
  spk(s);
}

如此，要满足：1.包含继承 2.重写父类函数
使用时形参为父类的引用/指针

虚函数的用法

//可将整体的类拆分，方便后续的修改和添加
class father
{
  public:
  virtual void speak()
  {
    cout<<"father!";
  }
};
class son1:public father
{
  public:
   void speak()
  {
    cout<<"son1!";
  }
};
class son2:public father
{
  public:
   void speak()
  {
    cout<<"son2!";
  }
};
int main()
{
  father * a=new son1;
  a->speak();
  a=new son2;
  a->speak();
  delete a;//指针类写法
}
//如上，可随时增添子类

纯虚函数

//虚析构
class father
{
  public:
  virtual void speak()=0;
};
class son1:public father
{
  public:
   void speak()
  {
    cout<<"son1!";
  }
};
class son2:public father
{
  public:
   void speak()
  {
    cout<<"son2!";
  }
};
int main()
{
  father * a=new son1;
  a->speak();
  a=new son2;
  a->speak();
  delete a;
}
//将father转化为纯虚函数后只能通过赋值的形式得到father的对象
//其子类必须重写该虚函数
//抽象类：只作为接口和过渡，用指针接收后调用对应的接口，如
class cc
{
    public：
        virtual int caclute()
    {
        return 0;
    }
}
class cb:public cc;
    class cb：public cc;

纯虚析构函数

class father
{
  public:
  father ()
  {
    cout<<"大的活了"<<endl;
  }
   virtual ~father()=0;
  virtual void speak()=0;
};
class son1:public father
{
  public:
   void speak()
  {
    cout<<"son1!";
  }
  son1 ()
  {
    cout<<"小的活了"<<endl;
  }
  ~son1()
  {
    cout<<"小的似了"<<endl;
  }
};
father::~father()
{
    
}//纯虚析构必须要补定义
int main()
{
  father * a=new son1;
  a->speak();
  delete a;
}