diff --git a/include/nlohmann/json.hpp b/include/nlohmann/json.hpp index 2ca029dd1..500acb36e 100644 --- a/include/nlohmann/json.hpp +++ b/include/nlohmann/json.hpp @@ -2838,50 +2838,53 @@ class basic_json /// @{ /*! - @brief get special-case overload + @brief get a pointer value (implicit) - This overloads avoids a lot of template boilerplate, it can be seen as the - identity method + Implicit pointer access to the internally stored JSON value. No copies are + made. - @tparam BasicJsonType == @ref basic_json + @warning Writing data to the pointee of the result yields an undefined + state. - @return a copy of *this + @tparam PointerType pointer type; must be a pointer to @ref array_t, @ref + object_t, @ref string_t, @ref boolean_t, @ref number_integer_t, + @ref number_unsigned_t, or @ref number_float_t. Enforced by a static + assertion. + + @return pointer to the internally stored JSON value if the requested + pointer type @a PointerType fits to the JSON value; `nullptr` otherwise @complexity Constant. - @since version 2.1.0 + @liveexample{The example below shows how pointers to internal values of a + JSON value can be requested. Note that no type conversions are made and a + `nullptr` is returned if the value and the requested pointer type does not + match.,get_ptr} + + @since version 1.0.0 */ - template::type, basic_json_t>::value, - int> = 0> - basic_json get() const + template::value, int>::type = 0> + auto get_ptr() noexcept -> decltype(std::declval().get_impl_ptr(std::declval())) { - return *this; + // delegate the call to get_impl_ptr<>() + return get_impl_ptr(static_cast(nullptr)); } /*! - @brief get special-case overload - - This overloads converts the current @ref basic_json in a different - @ref basic_json type - - @tparam BasicJsonType == @ref basic_json - - @return a copy of *this, converted into @tparam BasicJsonType - - @complexity Depending on the implementation of the called `from_json()` - method. - - @since version 3.2.0 + @brief get a pointer value (implicit) + @copydoc get_ptr() */ - template < typename BasicJsonType, detail::enable_if_t < - !std::is_same::value&& - detail::is_basic_json::value, int > = 0 > - BasicJsonType get() const + template < typename PointerType, typename std::enable_if < + std::is_pointer::value&& + std::is_const::type>::value, int >::type = 0 > + constexpr auto get_ptr() const noexcept -> decltype(std::declval().get_impl_ptr(std::declval())) { - return *this; + // delegate the call to get_impl_ptr<>() const + return get_impl_ptr(static_cast(nullptr)); } + private: /*! @brief get a value (explicit) @@ -2923,21 +2926,12 @@ class basic_json */ template < typename ValueTypeCV, typename ValueType = detail::uncvref_t, detail::enable_if_t < - !detail::is_basic_json::value && - detail::has_from_json::value && - !detail::has_non_default_from_json::value, + detail::is_default_constructible::value && + detail::has_from_json::value, int > = 0 > - ValueType get() const noexcept(noexcept( - JSONSerializer::from_json(std::declval(), std::declval()))) + ValueType get_impl(detail::priority_tag<0> /*unused*/) const noexcept(noexcept( + JSONSerializer::from_json(std::declval(), std::declval()))) { - // we cannot static_assert on ValueTypeCV being non-const, because - // there is support for get(), which is why we - // still need the uncvref - static_assert(!std::is_reference::value, - "get() cannot be used with reference types, you might want to use get_ref()"); - static_assert(std::is_default_constructible::value, - "types must be DefaultConstructible when used with get()"); - ValueType ret; JSONSerializer::from_json(*this, ret); return ret; @@ -2975,15 +2969,142 @@ class basic_json @since version 2.1.0 */ template < typename ValueTypeCV, typename ValueType = detail::uncvref_t, - detail::enable_if_t < !std::is_same::value && - detail::has_non_default_from_json::value, - int > = 0 > - ValueType get() const noexcept(noexcept( - JSONSerializer::from_json(std::declval()))) + detail::enable_if_t < + detail::has_non_default_from_json::value, + int > = 0 > + ValueType get_impl(detail::priority_tag<1> /*unused*/) const noexcept(noexcept( + JSONSerializer::from_json(std::declval()))) { + return JSONSerializer::from_json(*this); + } + + /*! + @brief get special-case overload + + This overloads converts the current @ref basic_json in a different + @ref basic_json type + + @tparam BasicJsonType == @ref basic_json + + @return a copy of *this, converted into @tparam BasicJsonType + + @complexity Depending on the implementation of the called `from_json()` + method. + + @since version 3.2.0 + */ + template < typename BasicJsonType, detail::enable_if_t < + detail::is_basic_json::value, + int > = 0 > + BasicJsonType get_impl(detail::priority_tag<2> /*unused*/) const + { + return *this; + } + + /*! + @brief get special-case overload + + This overloads avoids a lot of template boilerplate, it can be seen as the + identity method + + @tparam BasicJsonType == @ref basic_json + + @return a copy of *this + + @complexity Constant. + + @since version 2.1.0 + */ + template::value, + int> = 0> + basic_json get_impl(detail::priority_tag<3> /*unused*/) const + { + return *this; + } + + /*! + @brief get a pointer value (explicit) + @copydoc get() + */ + template::value, int> = 0> + constexpr auto get_impl(detail::priority_tag<4> /*unused*/) const noexcept + -> decltype(std::declval().template get_ptr()) + { + // delegate the call to get_ptr + return get_ptr(); + } + + public: + /*! + @brief get a (pointer) value (explicit) + + Performs explicit type conversion between the JSON value and a compatible value if required. + + - If the requested type is a pointer to the internally stored JSON value that pointer is returned. + No copies are made. + + - If the requested type is the current @ref basic_json, or a different @ref basic_json convertible + from the current @ref basic_json. + + - Otherwise the value is converted by calling the @ref json_serializer `from_json()` + method. + + @tparam ValueTypeCV the provided value type + @tparam ValueType the returned value type + + @return copy of the JSON value, converted to @tparam ValueType if necessary + + @throw what @ref json_serializer `from_json()` method throws if conversion is required + + @since version 2.1.0 + */ + template < typename ValueTypeCV, typename ValueType = detail::uncvref_t> + constexpr auto get() const noexcept(noexcept(get_impl(detail::priority_tag<4> {}))) + -> decltype(get_impl(detail::priority_tag<4> {})) + { + // we cannot static_assert on ValueTypeCV being non-const, because + // there is support for get(), which is why we + // still need the uncvref static_assert(!std::is_reference::value, "get() cannot be used with reference types, you might want to use get_ref()"); - return JSONSerializer::from_json(*this); + return get_impl(detail::priority_tag<4> {}); + } + + /*! + @brief get a pointer value (explicit) + + Explicit pointer access to the internally stored JSON value. No copies are + made. + + @warning The pointer becomes invalid if the underlying JSON object + changes. + + @tparam PointerType pointer type; must be a pointer to @ref array_t, @ref + object_t, @ref string_t, @ref boolean_t, @ref number_integer_t, + @ref number_unsigned_t, or @ref number_float_t. + + @return pointer to the internally stored JSON value if the requested + pointer type @a PointerType fits to the JSON value; `nullptr` otherwise + + @complexity Constant. + + @liveexample{The example below shows how pointers to internal values of a + JSON value can be requested. Note that no type conversions are made and a + `nullptr` is returned if the value and the requested pointer type does not + match.,get__PointerType} + + @sa @ref get_ptr() for explicit pointer-member access + + @since version 1.0.0 + */ + template::value, int>::type = 0> + auto get() noexcept -> decltype(std::declval().template get_ptr()) + { + // delegate the call to get_ptr + return get_ptr(); } /*! @@ -3056,101 +3177,6 @@ class basic_json return v; } - - /*! - @brief get a pointer value (implicit) - - Implicit pointer access to the internally stored JSON value. No copies are - made. - - @warning Writing data to the pointee of the result yields an undefined - state. - - @tparam PointerType pointer type; must be a pointer to @ref array_t, @ref - object_t, @ref string_t, @ref boolean_t, @ref number_integer_t, - @ref number_unsigned_t, or @ref number_float_t. Enforced by a static - assertion. - - @return pointer to the internally stored JSON value if the requested - pointer type @a PointerType fits to the JSON value; `nullptr` otherwise - - @complexity Constant. - - @liveexample{The example below shows how pointers to internal values of a - JSON value can be requested. Note that no type conversions are made and a - `nullptr` is returned if the value and the requested pointer type does not - match.,get_ptr} - - @since version 1.0.0 - */ - template::value, int>::type = 0> - auto get_ptr() noexcept -> decltype(std::declval().get_impl_ptr(std::declval())) - { - // delegate the call to get_impl_ptr<>() - return get_impl_ptr(static_cast(nullptr)); - } - - /*! - @brief get a pointer value (implicit) - @copydoc get_ptr() - */ - template < typename PointerType, typename std::enable_if < - std::is_pointer::value&& - std::is_const::type>::value, int >::type = 0 > - constexpr auto get_ptr() const noexcept -> decltype(std::declval().get_impl_ptr(std::declval())) - { - // delegate the call to get_impl_ptr<>() const - return get_impl_ptr(static_cast(nullptr)); - } - - /*! - @brief get a pointer value (explicit) - - Explicit pointer access to the internally stored JSON value. No copies are - made. - - @warning The pointer becomes invalid if the underlying JSON object - changes. - - @tparam PointerType pointer type; must be a pointer to @ref array_t, @ref - object_t, @ref string_t, @ref boolean_t, @ref number_integer_t, - @ref number_unsigned_t, or @ref number_float_t. - - @return pointer to the internally stored JSON value if the requested - pointer type @a PointerType fits to the JSON value; `nullptr` otherwise - - @complexity Constant. - - @liveexample{The example below shows how pointers to internal values of a - JSON value can be requested. Note that no type conversions are made and a - `nullptr` is returned if the value and the requested pointer type does not - match.,get__PointerType} - - @sa @ref get_ptr() for explicit pointer-member access - - @since version 1.0.0 - */ - template::value, int>::type = 0> - auto get() noexcept -> decltype(std::declval().template get_ptr()) - { - // delegate the call to get_ptr - return get_ptr(); - } - - /*! - @brief get a pointer value (explicit) - @copydoc get() - */ - template::value, int>::type = 0> - constexpr auto get() const noexcept -> decltype(std::declval().template get_ptr()) - { - // delegate the call to get_ptr - return get_ptr(); - } - /*! @brief get a reference value (implicit)