详解C++中的成员访问运算符和指针到成员运算符

// expre_Selection_Operator.cpp
// compile with: /EHsc
#include <iostream>
using namespace std;

struct Date {
  Date(int i, int j, int k) : day(i), month(j), year(k){}
  int month;
  int day;
  int year;
};

int main() {
  Date mydate(1,1,1900);
  mydate.month = 2;  
  cout << mydate.month << "/" << mydate.day
     << "/" << mydate.year << endl;

  Date *mydate2 = new Date(1,1,2000);
  mydate2->month = 2;
  cout << mydate2->month << "/" << mydate2->day
     << "/" << mydate2->year << endl;
  delete mydate2;
}

2/1/1900
2/1/2000

// expre_Expressions_with_Pointer_Member_Operators.cpp
// compile with: /EHsc
#include <iostream>

using namespace std;

class Testpm {
public:
  void m_func1() { cout << "m_func1\n"; }
  int m_num;
};

// Define derived types pmfn and pmd.
// These types are pointers to members m_func1() and
// m_num, respectively.
void (Testpm::*pmfn)() = &Testpm::m_func1;
int Testpm::*pmd = &Testpm::m_num;

int main() {
  Testpm ATestpm;
  Testpm *pTestpm = new Testpm;

// Access the member function
  (ATestpm.*pmfn)();
  (pTestpm->*pmfn)();  // Parentheses required since * binds
            // less tightly than the function call.

// Access the member data
  ATestpm.*pmd = 1;
  pTestpm->*pmd = 2;

  cout << ATestpm.*pmd << endl
     << pTestpm->*pmd << endl;
  delete pTestpm;
}
Output
m_func1
m_func1

1
2

// expre_Expressions_with_Pointer_Member_Operators2.cpp
// C2440 expected
class BaseClass {
public:
  BaseClass(); // Base class constructor.
  void Func1();
};

// Declare a pointer to member function Func1.
void (BaseClass::*pmfnFunc1)() = &BaseClass::Func1;

class Derived : public BaseClass {
public:
  Derived(); // Derived class constructor.
  void Func2();
};

// Declare a pointer to member function Func2.
void (Derived::*pmfnFunc2)() = &Derived::Func2;

int main() {
  BaseClass ABase;
  Derived ADerived;

  (ABase.*pmfnFunc1)();  // OK: defined for BaseClass.
  (ABase.*pmfnFunc2)();  // Error: cannot use base class to
              // access pointers to members of
              // derived classes. 

  (ADerived.*pmfnFunc1)();  // OK: Derived is unambiguously
               // derived from BaseClass. 
  (ADerived.*pmfnFunc2)();  // OK: defined for Derived.
}