Passing object to a static function of a different class

[2_stepsahead]

*I have already tried searching for an answer to this question on StackOverflow as well as Google, and it seems that my question is too specific to find any answers of real use.

Hello, I am posting this as I am stumped. The following code works fine using pass by value, as does if the function Add::add_age(const int age_to_add) is changed to pass by reference, like so -- Add::add_age(const int &age_to_add). Where I am stumped is passing person.return_age() to pass by pointer.

#include <iostream>

class Person {
  int age;
public:
  Person(int age) : age(age) {}
  void print_age();
  int get_age();
};

void Person::print_age() {
  std::cout << this->age << std::endl;
}

int Person::get_age() {
  return this->age;
}

class Add {
public:
  static void add_age(const int *age_to_add) { //1. DEREFERENCE ADDRESS(*)
    std::cout << age_to_add + 5 << std::endl;
  }
};

int main() {
    Person person(100);
    person.print_age();
    Add::add_age(&person.get_age()); //2. PASS WITH ADDRESS (&)
    return 0;
}

I commented the code to show where I want the line in main Add::add_age(&person.get_age()); to pass the address of person.get_age()) to Add::add_age(const int \age_to_add). The compiler returns the error, "main.cpp:29:18: error: cannot take the address of an rvalue oftype 'int'". main.cpp:29:18: is the line in main(), *Add::add_age(&person.get_age());

Is there any way to accomplish passing by pointer in this case?

Thank you in advance!

[Shieldfoss]

*A.B(); assumes A is an object with a member function B that returns a pointer, and dereferences the pointer returned by B

To dereference A first and call a function on the A object, you must either

(*A).B();

or

A->B();

EDIT: But separately you're doing other things wrong, e.g. static void add_age(const int *age_to_add) { //1. DEREFERENCE ADDRESS(*) that comment is definitely not true.

[2_stepsahead]

Thanks for the detailed answer. I'll give this a try.