The following code example is taken from the book
C++17 - The Complete Guide by Nicolai M. Josuttis, Leanpub, 2017
The code is licensed under a Creative Commons Attribution 4.0 International License. Creative Commons License

// raw code

#include "customer1.hpp"
#include <utility>  // for tuple-like API

// provide a tuple-like API for class Customer for structured bindings:
struct std::tuple_size<Customer> {
  static constexpr int value = 3;   // we have 3 attributes

struct std::tuple_element<2, Customer> {
  using type = long;                // last attribute is a long
template<std::size_t Idx>
struct std::tuple_element<Idx, Customer> {
  using type = std::string;         // the other attributes are strings

// define specific getters:
template<std::size_t> auto get(const Customer& c);
template<> auto get<0>(const Customer& c) { return c.getFirst(); }
template<> auto get<1>(const Customer& c) { return c.getLast(); }
template<> auto get<2>(const Customer& c) { return c.getValue(); }