get() [3/4]

template<typename Target , product_type T>

decltype(auto) constexpr get ( T &&  t )

related

Extracts the value with type Target of a kumi::product_type.

Note

This function is not callable on a product_type with duplicate types. It is provided as an utility for User Defined Types, kumi types have their own overloads.

Template Parameters

Target	The type of the field to extract from the product type.
T	the type of the product_type from which to the field.

Parameters

t	the product_type from which to the field.

Returns

A references to the values of a kumi::product_type.

Example:

 
#include <kumi/kumi.hpp>
#include <iostream>
#include <string>
 
namespace ns
{
  struct people
  {
    std::string name;
    int         age;
  };
 
  template<std::size_t I>
  decltype(auto) get(people const& s) noexcept
  {
    if constexpr(I==0) return s.name;
    if constexpr(I==1) return s.age;
  }
 
  template<std::size_t I>
  decltype(auto) get(people& s) noexcept
  {
    if constexpr(I==0) return s.name;
    if constexpr(I==1) return s.age;
  }
}
 
// Opt-in for Product Type semantic
template<>
struct kumi::is_product_type<ns::people> : std::true_type
{};
 
// Adapt as structured bindable type
template<>
struct  std::tuple_size<ns::people>
      : std::integral_constant<std::size_t,2> {};
 
template<> struct std::tuple_element<0,ns::people> { using type = std::string;  };
template<> struct std::tuple_element<1,ns::people> { using type = int;          };
 
int main()
{
  ns::people peter{"Peter Parker", 24};
    
  std::cout << kumi::get<std::string> (peter) << "\n";
  std::cout << kumi::get<int>         (peter) << "\n";
}