Initialising References in a class

Unassigned references cannot exist for a class. There is no C++ concept of an "unassigned reference" and the behavior of any program that has one is undefined. If a class contains a reference then it must be initialised through an initialiser list. You can't declare a reference variable in the class and then assign it later on. Non-reference variables and pointers can be left uninitialised but references must have a value upon entry. The only way to do this is through an initialiser.

//Program tested on Microsoft Visual Studio 2008 - Zahid Ghadialy
//Example showing initializing of refrences in a class
#include<iostream>

using namespace std;

class A
{
public:
  A(string &name);
  void print()
  {
    cout<<"a = "<<a<<" and s = "<<s.c_str()<<endl;
  }
  void set_a(int x) {a = x;}
private:
  A(); //Shouldnt really be called because we need to have a reference
  int a;
  string &s;
};

A::A(string &name): s(name)
{
  //s = name; - error. Should be in initialiser
  a = 0;
}

int main()
{
  string z = "zahid";
  A a(z);
  a.print();
  z = "christian";
  a.print();
  a.set_a(30);
  a.print();
  return 0;
}

The output is as follows: