Concept Of Friend Function Through Reference Class Object

#include <iostream>
using namespace std;
class B;
class A
{int a;
public:
   void set_val (int x ){
a=x;  }
    friend void swap1(A &obj1 ,B &obj2);};
class B{
int b;
public:
   friend void swap1 (A &obj1 ,B &obj2);
void set_val (int y ){
b=y;}};
void  swap1 (A &obj1, B &obj2)
{int temp;
temp =obj1.a  ;
obj1 . a=obj2.b;
obj2.b = temp;
       cout << "The value of a :"<<  obj1.a  << endl;
       cout <<  "The value of b :"<< obj2.b  << endl;}

int main(){
  A obj;
    B o;
    obj.set_val (5);
o.set_val(2);
swap1 (obj,o);
    return 0;}
Output: