How to call a setter function from one class in another class?

Question

I'm trying to call the setter function from Class A in class B but I'm unable to do this and I don't know why. (I'm a beginner in C++ and I need to do this as it's related to my assignment.)

Here is my code:

#include <iostream>

using namespace std;

class A{
private:
  int i = 2;
public:
  int getInt(){
    return i;
  };
  void setI(int a){
    i = a;
  }
};

class B{
private:
  int c = 3;
public:
  void setAI(A a){
    a.setI(c);
  }
};

int main() {
  A a;
  B b;

  cout << a.getInt() << endl;
  b.setAI(a);
  cout << a.getInt() << endl;
  a.setI(5);
  cout << a.getInt() << endl;
}

The output I'm getting is:

2
2
5

When I want to get:

2
3
5

Answer 1

I just made some changes in the setAI() function. I have passed the object by address rather than value. I'm not sure of what was causing the problem (as I'm also a beginner) but the pointer has solved the problem.

#include <iostream>

using namespace std;

class A{
private:
  int i = 2;
public:
  int getInt(){
    return i;
  };
  void setI(int a){
    i = a;
  }
};

class B{
private:
  int c = 3;
public:
  void setAI(A *a){
      a->setI(c);
  }
};

int main() {
  A a;
  B b;

  cout << a.getInt() << endl;
  b.setAI(&a);
  cout << a.getInt() << endl;
  a.setI(5);
  cout << a.getInt() << endl;
}