C++ friend Keyword

class Person {
  private:
    int age;
  public:
    Person(int a) {
      age = a;
    }
    friend void printAge(Person p);
};

void printAge(Person p) {
  cout << "Age: " << p.age;
}

int main() {
  Person myObj(30);
  printAge(myObj);         // OK
  // cout << myObj.age;    // Error, because age is private
  return 0;
}

Definition and Usage

The friend keyword gives a function or another class access to the private and protected members of a class. The class decides who its friends are, with a friend declaration inside the class.

A friend function is not a member of the class. You call it like a normal function, like printAge(myObj), not with a dot.

To make a whole class a friend, write friend class and the name of the class, like friend class Car;.

Related Pages

Read more about friend functions in our C++ Friend Functions Tutorial.