getters and setters for nested structs

getters-and-setters.cpp

#include <utility>
#include <iostream>

template <typename Retval, typename T>
auto make_ref(Retval T::*prop) {
    return [=](T &obj) -> Retval& { return obj.*prop; };
}

template <typename Retval, typename T, typename... Args>
auto make_ref(Retval T::*prop, Args... args) {
    auto step = make_ref(args...);
    return [=](T &obj) -> auto& { return step(obj.*prop); };
}

template <typename Retval, typename T, typename... Args>
auto make_getter(Retval T::*prop, Args... args) {
    auto ref = make_ref(prop, args...);
    return [=](T const &obj) -> auto const & { return ref(const_cast<T&>(obj)); };
}

template <typename Retval, typename T, typename... Args>
auto make_setter(Retval T::*prop, Args... args) {
    auto ref = make_ref(prop, args...);
    return [=](T &obj, auto val) -> void { ref(obj) = val; };
}

struct Atom {
    int protons;
};

struct Child {
    Atom atom;
};

struct Parent {
    Child child;
};

int main() {
    Parent parent{{{0}}};
    auto ref = make_ref(&Parent::child, &Child::atom, &Atom::protons);
    auto setter = make_setter(&Parent::child, &Child::atom, &Atom::protons);
    auto getter = make_getter(&Parent::child, &Child::atom, &Atom::protons);
    
    int n = 0;
    std::cin >> n;
    ref(parent) = n;
    setter(parent, n);
    return getter(parent);
}