cannot call member function without object

Question

This program has the user input name/age pairs and then outputs them, using a class. Here is the code.

#include "std_lib_facilities.h"  class Name_pairs { public:        bool test();        void read_names();        void read_ages();        void print(); private:         vector<string>names;         vector<double>ages;         string name;         double age; };  void Name_pairs::read_names() {      cout << "Enter name: ";      cin >> name;      names.push_back(name);      cout << endl; }  void Name_pairs::read_ages() {      cout << "Enter corresponding age: ";      cin >> age;      ages.push_back(age);      cout << endl; }  void Name_pairs::print() {      for(int i = 0; i < names.size() && i < ages.size(); ++i)              cout << names[i] << " , " << ages[i] << endl; }  bool Name_pairs::test() {    int i = 0;    if(ages[i] == 0 || names[i] == "0") return false;    else{         ++i;         return true;} }   int main() {     cout << "Enter names and ages. Use 0 to cancel.\n";     while(Name_pairs::test())     {      Name_pairs::read_names();      Name_pairs::read_ages();      }      Name_pairs::print();      keep_window_open(); } 

However, in int main() when I'm trying to call the functions I get "cannot call 'whatever name is' function without object." I'm guessing this is because it's looking for something like variable.test or variable.read_names. How should I go about fixing this?

Answer 1

You need to instantiate an object in order to call its member functions. The member functions need an object to operate on; they can't just be used on their own. The main() function could, for example, look like this:

int main() {    Name_pairs np;    cout << "Enter names and ages. Use 0 to cancel.\n";    while(np.test())    {       np.read_names();       np.read_ages();    }    np.print();    keep_window_open(); } 

Answer 2

If you want to call them like that, you should declare them static.