Friend functions & class in OOPs

 #include <iostream>

using namespace std;

class A {

    string secret = "secret data";

    friend class B;

    friend void revealSecret(A &obj);

};

class B {  // becomes a friend class of A

public:

    void showSecret(A &obj) {

        cout << obj.secret << endl;

    }

};

void revealSecret(A &obj) {

    cout << obj.secret << endl;

}

int main() {

    A a1;

    B b1;

    // b1.showSecret(a1);

    revealSecret(a1);

    return 0;

}