Point to class member

#include <iostream>
using namespace std;

class Student
{
   public:
   Student(string n, int nu):name(n),num(nu){}
   string name;
   int num;
};

int main()
{
   Student s("zhangsi", 100);
   Student *ps = &s;

   Student ss("zhaoqi", 100);
   Student *pss = &ss;
//string *ps = &s.name;//the action destroy the encapsulation
//下面讲的指针,是指向类层面的指针,而不是对象层面
//要想使用,还要跟具体的对象产生关系
   string Student:: *psn = &Student::name;
   cout << s.*psn << endl;
   cout << ps->*psn << endl;

   cout << ss.*psn << endl;
   cout << pss->*psn << endl;

   return 0;
}

在c++中

.*：Pointer to member

->*:Pointer to member

Point to class function

#include <iostream>
using namespace std;

class Student
{
   public:
   Student(string n, int nu):name(n),num(nu){}
   void dis(int idx)
   {
       cout << "idx:" << idx << "name:" << name << "number:" << num << endl;
   }
   string name;
   int num;
};

int main()
{
    void (Student::*pdis)(int idx) = &Student::dis;
    Student s("zhangsan", 100);
    Student *ps = &s;
    Student ss("zhangsan", 100);
    Student *pss = &ss;
    (s.*pdis)(1);
    (ss.*pdis)(2);
    (ps->*pdis)(1);
    (ps->*pdis)(2);

    return 0;
}

test1:
#include <iostream>
using namespace std;

struct Point
{
    int add(int x, int y)
    {
        return x + y;
    }
    int minus(int x, int y)
    {
        return x - y;
    }
    int multi(int x, int y)
    {
        return x * y;
    }
    int div(int x, int y)
    {
        return x / y;
    }
};

int oper(Point &p, int (Point::*pf)(int x, int y), int x, int y)
{
    return (p.*pf)(x,y);
}
typedef int (Point::*PF)(int x, int y);
int main()
{
    Point p;
    PF pf = &Point::add;
    cout << oper(p, pf, 1, 2);
    return 0;
}

 更加隐蔽的接口

#include <iostream>
using namespace std;
class Game
{
   public:
      Game()
      {
         pf[0] = &Game::f;
         pf[1] = &Game::g;
         pf[2] = &Game::h;
         pf[3] = &Game::l;
      }
     void select(int i)
     {
        if (i >= 0 && i <= 3)
        {
           (this->*pf[i])(i);
        }
     }
   private:
     void f(int idx) { cout << "void f(int idx)" << "idx:" << idx << endl; }
     void g(int idx) { cout << "void g(int idx)" << endl; }
     void h(int idx) { cout << "void h(int idx)" << endl; }
     void l(int idx) { cout << "void l(int idx)" << endl; }
     enum{
        nc = 4
     };

     void (Game::*pf[nc])(int idx);  
};

int main()
{
   Game g;
   g.select(1);
   g.select(2);
   g.select(3);
   return 0;
}