operator[]() [4/4]

template<typename... Ts>

template<str Name>
requires (concepts::contains_label<label_t<Name>, Ts...>)

decltype(auto) kumi::record< Ts >::operator[] ( label_t< Name > l ) &

inlineconstexprnoexcept

Extracts the element of the field labeled L from a kumi::record.

Note

Does not participate in overload resolution if the label is not present in the record

Parameters

l	label of the field to access

Returns

A reference to the element of the selected field of current record.

Example:

#include <kumi/kumi.hpp>
#include <iostream>
 
struct my_id : kumi::identifier<my_id>
{
  using parent = kumi::identifier<my_id>;
  using parent::operator=;
 
  friend constexpr auto to_str(my_id) { return kumi::str{"mystery"}; }
};
 
inline constexpr my_id my_field{};
 
int main()
{
  using namespace kumi::literals;
 
  kumi::record r = { "x"_id = 1, "y"_id = 2.3, my_field = '@' };
  std::cout << r << "\n";
 
  std::cout << r["x"_l] << "\n";
  std::cout << r["y"_l] << "\n";
  std::cout << r["mystery"_l] << "\n";
 
  r["mystery"_l]++;
  std::cout << r["mystery"_l] << "\n";
}