C++ References

Creating a Reference

You create a reference by adding an ampersand (&) to the type when you declare the variable. The reference must be attached to an existing variable at the moment it is created.

#include <iostream>
#include <string>
using namespace std;

int main() {
  string food = "Pizza";
  string &meal = food;   // meal is a reference to food
  cout << food << "\n";
  cout << meal << "\n";
  return 0;
}
// Output:
// Pizza
// Pizza

They Share the Same Value

Because a reference and its variable are the same thing under two names, updating either one updates both. This is different from copying a value, where the copy would be independent.

#include <iostream>
#include <string>
using namespace std;

int main() {
  string food = "Pizza";
  string &meal = food;
  meal = "Burger";   // change through the reference
  cout << food;      // the original also changed
  return 0;
}
// Output: Burger

Rules to Remember

• A reference must be initialized when it is declared; you cannot create an empty reference.
• Once bound to a variable, a reference can never be changed to refer to a different variable.
• A reference is not a copy; it shares the same memory as the original.