friend function with template classes not working

general
, ,
1

This program shows me some unknown linker error. What could be wrong?

Error:

 Undefined symbols for architecture x86_64:
 "totalIncome(Husband<int>, Wife<int>)", referenced from:
       _main in main.cpp.o



#include <iostream>

using namespace std;

template<typename T> class Wife;           // Forward declaration of template class : Wife

template<typename T>
        class Husband{
        friend void totalIncome(Husband<T> hobj, Wife<T> wobj);

        public:
            Husband() = default;
            Husband(T new_salary): salary{new_salary} {}

        private:
            T salary;
        };

template<typename T>
        class Wife{
        friend void totalIncome(Husband<T> hobj, Wife<T> wobj);

        public:
            Wife() = default;
            Wife(T new_salary): salary{new_salary} {}

        private:
            T salary;
        };

template<typename T> void totalIncome(Husband<T> hobj, Wife<T> wobj)
{
    cout << "Total Income of Husband & Wife: ";
    cout << hobj.salary + wobj.salary;
}

int main()
{
    Husband<int> h(40000);
    Wife<int> w(90000);

    totalIncome(h, w);

    return 0;
}
2

what is typename you used in template. I use ‘class’ keyword instead of typename

3

That’s in new standard…also please, use comments for asking questions. Don’t answer. Delete this answer.