How to iterate over non-const variables in C++?

Question

#include <initializer_list>

struct Obj {
    int i;
};

Obj a, b;

int main() {
    for(Obj& obj : {a, b}) {
        obj.i = 123;   
    }
}

This code does not compile because the values from the initializer_list {a, b} are taken as const Obj&, and cannot be bound to the non-const reference obj.

Is there a simple way to make a similar construct work, i.e. iterate over values that are in different variables, like a and b here.

Answer 1

It does not work because in {a,b} you are making a copy of a and b. One possible solution would be to make the loop variable a pointer, taking the addresses of a and b:

#include <initializer_list>

struct Obj {
    int i;
};

Obj a, b;

int main() {
    for(auto obj : {&a, &b}) {
        obj->i = 123;   
    }
}

See it live

Note: it is generically better to use auto, as it could avoid silent implicit conversions