class has no member from hpp definition code example

Example: No member named 'empty' in 'Patient'

for (size_t k{0}; k < 12; k++){
        for (size_t l{0}; l < 5; l++){
            if (weeklyAppointments[k][l]->empty() != false){
                cout << weeklyAppointments[k][l]->get_patient_name() << "\t\t\t\t";
            }
            else{
                cout << *(*(weeklyAppointments+(k))+(l))
            }
        }