protected_friend_class_function.cpp

#include <iostream>
#include <memory>
/*
You can only access protected members in instances of your type (or derived from
your type). You cannot access protected members of an instance of a parent or
cousin type.
*/

class base {
  friend class frindClass;
  friend void friendFunction(int y);

private:
  int x;
  void privateMethod() { std::cout << "privateMethod from base" << std::endl; }

protected:
  void info() { std::cout << "info from base" << std::endl; }

public:
  base(int x) : x(x){};
  void print() { std::cout << "base" << std::endl; }
};

class derived : public base {
public:
  derived(int x) : base(x){};
  void print() { std::cout << "derived" << std::endl; }
  void infoCaller() { info(); }
};

void friendFunction(int y) {
  base baseObject(5);
  std::cout << baseObject.x + y << std::endl;
}

class frindClass {
  std::shared_ptr<base> b;

public:
  frindClass(int x) { b.reset(new base(x)); }
  void getinfo() {
    b->info();
    std::cout << b->x << std::endl;
  }
};
int main(int argc, char *argv[]) {

  base baseObject(5);
  /*This will give you an error*/
  // baseObject.info();

  derived derivedObject(10);
  /*This will give you an error*/
  // derivedObject.info();

  std::cout << "The correct way to call a protectd method from base class in "
               "derived class"
            << std::endl;
  derivedObject.infoCaller();

  std::cout << "Accessing private member in a friend function" << std::endl;
  int y = 3;
  friendFunction(y);

  std::cout << "Accessing private member in a friend class" << std::endl;
  frindClass frindClassObject(y);
  frindClassObject.getinfo();

  return 0;
}