add alias templates to reduce boilerplate
This commit is contained in:
Théo DELRIEU
Théo DELRIEU
parent
fe628b585b
commit
d54d6bb84c
1 changed files with 49 additions and 43 deletions
92
src/json.hpp
92
src/json.hpp
|
|
@ -117,6 +117,17 @@ namespace nlohmann
|
|||
template <typename T, typename = void>
|
||||
struct json_traits;
|
||||
|
||||
// alias templates to reduce boilerplate
|
||||
template <bool B, typename T = void>
|
||||
using enable_if_t = typename std::enable_if<B, T>::type;
|
||||
|
||||
template <typename T>
|
||||
using remove_cv_t = typename std::remove_cv<T>::type;
|
||||
|
||||
template <typename T>
|
||||
using remove_reference_t = typename std::remove_reference<T>::type;
|
||||
|
||||
// TODO update this doc
|
||||
/*!
|
||||
@brief unnamed namespace with internal helper functions
|
||||
@since version 1.0.0
|
||||
|
|
@ -1393,15 +1404,11 @@ class basic_json
|
|||
// auto j = json{{"a", json(not_equality_comparable{})}};
|
||||
//
|
||||
// we can remove this constraint though, since lots of ctor are not explicit already
|
||||
template <
|
||||
typename T,
|
||||
typename =
|
||||
typename std::enable_if<detail::has_json_traits<typename std::remove_cv<
|
||||
typename std::remove_reference<T>::type>::type>::value>::type>
|
||||
template <typename T, typename = enable_if_t<detail::has_json_traits<
|
||||
remove_cv_t<remove_reference_t<T>>>::value>>
|
||||
explicit basic_json(T &&val)
|
||||
: basic_json(json_traits<typename std::remove_cv<
|
||||
typename std::remove_reference<T>::type>::type>::
|
||||
to_json(std::forward<T>(val))) {}
|
||||
: basic_json(json_traits<remove_cv_t<remove_reference_t<T>>>::to_json(
|
||||
std::forward<T>(val))) {}
|
||||
/*!
|
||||
@brief create a string (explicit)
|
||||
|
||||
|
|
@ -1418,14 +1425,15 @@ class basic_json
|
|||
|
||||
@sa @ref basic_json(const typename string_t::value_type*) -- create a
|
||||
string value from a character pointer
|
||||
@sa @ref basic_json(const CompatibleStringType&) -- create a string
|
||||
value
|
||||
@sa @ref basic_json(const CompatibleStringType&) -- create a string value
|
||||
from a compatible string container
|
||||
|
||||
@since version 1.0.0
|
||||
*/
|
||||
basic_json(const string_t &val) : m_type(value_t::string), m_value(val) {
|
||||
assert_invariant();
|
||||
basic_json(const string_t& val)
|
||||
: m_type(value_t::string), m_value(val)
|
||||
{
|
||||
assert_invariant();
|
||||
}
|
||||
|
||||
/*!
|
||||
|
|
@ -2763,17 +2771,12 @@ class basic_json
|
|||
|
||||
// get_impl overload chosen if json_traits struct is specialized for type T
|
||||
// simply returns json_traits<T>::from_json(*this);
|
||||
// TODO add alias templates (enable_if_t etc)
|
||||
template <
|
||||
typename T,
|
||||
typename = typename std::enable_if<
|
||||
detail::has_json_traits<typename std::remove_cv<
|
||||
typename std::remove_reference<T>::type>::type>::value>::type>
|
||||
auto get_impl(T *) const -> decltype(
|
||||
json_traits<typename std::remove_cv<typename std::remove_reference<
|
||||
T>::type>::type>::from_json(std::declval<basic_json>())) {
|
||||
return json_traits<typename std::remove_cv<
|
||||
typename std::remove_reference<T>::type>::type>::from_json(*this);
|
||||
template <typename T, typename = enable_if_t<detail::has_json_traits<
|
||||
remove_cv_t<remove_reference_t<T>>>::value>>
|
||||
auto get_impl(T *) const
|
||||
-> decltype(json_traits<remove_cv_t<remove_reference_t<T>>>::from_json(
|
||||
std::declval<basic_json>())) {
|
||||
return json_traits<remove_cv_t<remove_reference_t<T>>>::from_json(*this);
|
||||
}
|
||||
|
||||
// this one is quite atrocious
|
||||
|
|
@ -2781,31 +2784,34 @@ class basic_json
|
|||
// I chose to prefer the json_traits specialization if it exists, since it's a more advanced use.
|
||||
// But we can of course change this behaviour
|
||||
template <typename T>
|
||||
auto get_impl(T *) const -> typename std::enable_if<
|
||||
not detail::has_json_traits<typename std::remove_cv<T>::type>::value,
|
||||
typename std::remove_cv<typename std::remove_reference<
|
||||
decltype(::nlohmann::from_json(std::declval<basic_json>(),
|
||||
std::declval<T &>()),
|
||||
std::declval<T>())>::type>::type>::type
|
||||
auto get_impl(T *) const
|
||||
-> enable_if_t<not detail::has_json_traits<remove_cv_t<T>>::value,
|
||||
remove_cv_t<remove_reference_t<decltype(
|
||||
::nlohmann::from_json(std::declval<basic_json>(),
|
||||
std::declval<T &>()),
|
||||
std::declval<T>())>>>
|
||||
{
|
||||
typename std::remove_cv<typename std::remove_reference<T>::type>::type
|
||||
ret;
|
||||
remove_cv_t<T> ret;
|
||||
// I guess this output parameter is the only way to get ADL
|
||||
// Even if users can use the get<T> method to have a more 'functional' behaviour
|
||||
// i.e. having a return type, could there be a way to have the same behaviour with from_json?
|
||||
// e.g. auto t = nlohmann::from_json<T>(json{});
|
||||
// this seems to require variable templates though... (at least it did when I tried to implement it)
|
||||
::nlohmann::from_json(*this, ret);
|
||||
return ret;
|
||||
}
|
||||
|
||||
/// get an object (explicit)
|
||||
template <class T,
|
||||
typename std::enable_if<
|
||||
std::is_convertible<typename object_t::key_type,
|
||||
typename T::key_type>::value and
|
||||
std::is_convertible<basic_json_t,
|
||||
typename T::mapped_type>::value,
|
||||
int>::type = 0>
|
||||
T get_impl(T *) const {
|
||||
if (is_object()) {
|
||||
return T(m_value.object->begin(), m_value.object->end());
|
||||
} else {
|
||||
template<class T, typename std::enable_if<
|
||||
std::is_convertible<typename object_t::key_type, typename T::key_type>::value and
|
||||
std::is_convertible<basic_json_t, typename T::mapped_type>::value, int>::type = 0>
|
||||
T get_impl(T*) const
|
||||
{
|
||||
if (is_object())
|
||||
{
|
||||
return T(m_value.object->begin(), m_value.object->end());
|
||||
}
|
||||
else
|
||||
{
|
||||
|
||||
JSON_THROW(std::domain_error("type must be object, but is " + type_name()));
|
||||
}
|
||||
|
|
|
|||
Loading…
Reference in a new issue