f0905.cpp

it is a usefull thing

//=====================================
// f0905.cpp
// 对象成员的默认构造
//=====================================
#include<iostream>
using namespace std;
//-------------------------------------
class StudentID{
  int value;
public:
  StudentID(){
    static int nextStudentID = 0;
    value = ++nextStudentID;
    cout<<"Assigning student id "<<value<<"\n";
  }
};//-----------------------------------
class Student{
  string name;
  StudentID id;
public:
  Student(string n = "noName"){
    cout <<"Constructing student " + n + "\n";
    name = n;
  }
};//-----------------------------------
int main(){
  Student s("Randy");
}//====================================