std C ++ 11 :: bind perception of

Found that using std :: bind can achieve a good observer pattern in design mode before the query data.

But the called function bind bound more difficult to implement inheritance using multilevel pointer inheritance.

Sample code is as follows:

Compiler environment: VS2017

 1 #include "pch.h"
 2 #include <iostream>
 3 #include <vector>
 4 #include <functional>
 5 class Base
 6 {
 7 public:
 8     virtual void printMsg() { std::cout << "Base Class" << std::endl; }
 9 };
10 
11 class Derive :public Base
12 {
13 public:
14     virtual void printMsg() { std::cout << "Derive Class" << std::endl; }
15 };
16 
17 class TestClass
18 {
19 public:
20     void PrintMsg(Base **ppbase) { (*ppbase)->printMsg(); }
21 };
22 
23 int main()
24 {
25     std::vector<std::function<void(Base**)>>vec1;
26     TestClass *ptest = new TestClass();
27     Base* pbase = new Base();
28     Base* pder = new new Derive ();
 29      Base ** = & ppbase pbase; // increase subclass 
30      vec1.push_back (STD :: the bind (& the TestClass :: PrintMsg, PTEST, ppbase));
 31 is      * = ppbase PDER; // Assignment 
32      vec1 [ 0 ] (NULL);
 33 is  
34 is      return  0 ;
 35 }

If you delete lines 29 and 31, display Base Class, plus then display Derive Class. This is because at the time of the call, the pointer on the address already changed.