contains_only

contains_only_t kumi::contains_only {}

inlineconstexprnodiscardnoexcept

Callable object checking if a product type contains fields based on on selected identifier.

Header file

#include <kumi/algorithm/contains.hpp>

Call Signature

template<product_type T, identifier... IDs>
constexpr auto contains_only(T && t, IDs const&... ids) noexcept;

Parameters

• t: The product type to inspect
• ids: The identifiers to check for

Return value

• std::true_type if t contains a field labeled with any of the ids, std::false_type otherwise.

Helper type

    template<kumi::concepts::product_type T, kumi::concepts::identifier... IDs> struct contains_only
    {
      using type = decltype(kumi::contains_only(std::declval<T>(), std::declval<IDs>()...));
    };
 
    template<kumi::concepts::product_type T, kumi::concepts::identifier... IDs>
    using contains_only_t = typename kumi::result::contains_only<T, IDs...>::type;
 

Computes the return type of a call to kumi:contains_only

Examples

Tuple

#include <kumi/kumi.hpp>
#include <iostream>
 
using namespace kumi::literals;
 
template<kumi::concepts::product_type T>
void check_contains(T const&)
{
  if constexpr(kumi::contains_only(T{}, "value"_id, "active"_id))
    std::cout << "Correct product_type\n";
  else
    std::cout << "Incorrect product type\n";
}
 
int main()
{
  check_contains( kumi::tuple{"value"_id = 9  });
  check_contains( kumi::tuple{"malus"_id = 6.5, "value"_id = 17} );
  check_contains( kumi::tuple{"active"_id = std::bool_constant<true>{}     });
  check_contains( kumi::tuple{"active"_id = std::bool_constant<true>{}, "value"_id = 17} );
  check_contains( kumi::tuple{"active"_id = std::bool_constant<true>{}, "value"_id = 17, "other"_id = false});
}

Record

#include <kumi/kumi.hpp>
#include <iostream>
 
using namespace kumi::literals;
 
template<kumi::concepts::product_type T>
void check_contains(T const&)
{
  if constexpr(kumi::contains_only(T{}, "value"_id, "active"_id))
    std::cout << "Correct product_type\n";
  else
    std::cout << "Incorrect product type\n";
}
 
int main()
{
  check_contains( kumi::record{"value"_id = 9  });
  check_contains( kumi::record{"malus"_id = 6.5, "value"_id = 17} );
  check_contains( kumi::record{"active"_id = std::bool_constant<true>{}     });
  check_contains( kumi::record{"active"_id = std::bool_constant<true>{}, "value"_id = 17} );
  check_contains( kumi::record{"active"_id = std::bool_constant<true>{}, "value"_id = 17, "other"_id = false});
}