Qt C++ cannot call member function '~~ const' without object [duplicate] - c++

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.

Answer 3

just add static keyword at the starting of the function return type..
and then you can access the member function of the class without object:)
for ex:
static void Name_pairs::read_names()
{
cout << "Enter name: ";
cin >> name;
names.push_back(name);
cout << endl;
}

Answer 4

You are right - you declared a new use defined type (Name_pairs) and you need variable of that type to use it.
The code should go like this:
Name_pairs np;
np.read_names()