contains_only()

template<concepts::product_type T, concepts::identifier... Is>

auto kumi::contains_only ( T && t, Is const &... ids )

inlineconstexprnoexcept

Checks if a product type contains fields based only on selected identifiers.

Parameters

t	the product type to inspect.
ids	Identifiers to check

Returns

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

Helper type

namespace kumi::result
{
  template<product_type T, concepts::identifier... ID> struct contains_only;
 
  template<product_type T, concepts::identifier... ID>
  using contains_only_t = typename contains_only<T,ID...>::type;
}

Computes the type returned by a call to 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(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(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});
}