naming a member of a struct with a string array

Question

in a Project of mine i need to call a member/property (dont know the right term) of a struct by a string which is inside an array.

The fat part in the line with the comment //???? is the Problem users[i].members[j] is nonsense and i know that but i just cant figure out what would be right there.

Thanks for your help in advance :D

struct person {         // Eigenschaften des Eintrags
    string name;        //nachname
    string vorname;     //vorname
    string telefon;     // telfonnummer
};
const int numbr_struct_att = 3;
const string members[numbr_struct_att] = { "name","vorname","telefon" };   

 
cout << setw(5) << left << "Index" << setw(20) << left << "Name" << setw(20) << left << "Vorname" << setw(20) << left << "Telefon" << endl;                           // Header
        for (int i = 0; i <= usernum; i++) {
            cout << setw(5) << left << i+1;
            for (int j = 0; j < numbr_struct_att; j++) {
                cout << setw(20) << left << users[i].members[j] // ?????
            }
            cout << endl;
        }

c++ has no reflection you cannot iterate members of a type. unless you do put them inside an array of course — 463035818_is_not_an_ai
– 463035818_is_not_an_ai, Commented Sep 8, 2020 at 17:39
I appreciate that you are forthcoming about not knowing the right terms for things and took a reasonable shot at describing what you want even though you don't know how to do it. I realize it's difficult to ask questions like this when you don't know what you're looking for. But as a word of advice, don't let the code speak entirely for itself. Describe, in words, what you are trying to accomplish and what you are hoping your results to be. — Wyck
– Wyck, Commented Sep 8, 2020 at 17:52

KamilCuk · Accepted Answer · 2020-09-08 17:47:22Z

3

Create a map of strings to member pointers.

#include <map>
#include <string>
#include <iostream>
struct person {         // Eigenschaften des Eintrags
    std::string name;        //nachname
    std::string vorname;     //vorname
    std::string telefon;     // telfonnummer
};

// map names of variables to person member pointers to strings
std::map<std::string, std::string person::*> somemap{
     { "name", &person::name },
     { "vorname", &person::vorname },
};

// then just get the member pointers and call it on a instance of a person:
int main() {
    person myperson{"my name"};
    std::string I_choose_you = "name";
    std::string persons_name = myperson.*somemap.find(I_choose_you)->second;
    std::cout << persons_name << "\n";
}

Godbolt link

answered Sep 8, 2020 at 17:47

KamilCuk

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