Passing References to Objects : object pointer « Class « C++ Tutorial

1. C++ Tutorial
2. Class
3. object pointer

#include <iostream>
using namespace std;
   
class MyClass {
  int id;
public:
  int i;
  MyClass(int i);
  ~MyClass();
  void neg(MyClass &o) { o.i = -o.i; } // no temporary created
};
   
MyClass::MyClass(int num)
{
  cout << "Constructing " << num << "\n";
  id = num;
}
   
MyClass::~MyClass()
{
  cout << "Destructing " << id << "\n";
}
   
int main()
{
  MyClass o(1);
   
  o.i = 10;
  o.neg(o);
   
  cout << o.i << "\n";
   
  return 0;
}