mirror of
https://github.com/nlohmann/json
synced 2024-11-22 12:00:05 +00:00
Refactor json::get() to use priority_tag.
This commit is contained in:
Anthony VH
parent
6278f31d23
commit
6ef1614fa9
@ -2838,50 +2838,53 @@ class basic_json
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/// @{
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/*!
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@brief get special-case overload
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@brief get a pointer value (implicit)
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This overloads avoids a lot of template boilerplate, it can be seen as the
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identity method
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Implicit pointer access to the internally stored JSON value. No copies are
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made.
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@tparam BasicJsonType == @ref basic_json
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@warning Writing data to the pointee of the result yields an undefined
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state.
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@return a copy of *this
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@tparam PointerType pointer type; must be a pointer to @ref array_t, @ref
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object_t, @ref string_t, @ref boolean_t, @ref number_integer_t,
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@ref number_unsigned_t, or @ref number_float_t. Enforced by a static
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assertion.
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@return pointer to the internally stored JSON value if the requested
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pointer type @a PointerType fits to the JSON value; `nullptr` otherwise
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@complexity Constant.
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@since version 2.1.0
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@liveexample{The example below shows how pointers to internal values of a
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JSON value can be requested. Note that no type conversions are made and a
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`nullptr` is returned if the value and the requested pointer type does not
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match.,get_ptr}
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@since version 1.0.0
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*/
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template<typename BasicJsonType, detail::enable_if_t<
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std::is_same<typename std::remove_const<BasicJsonType>::type, basic_json_t>::value,
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int> = 0>
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basic_json get() const
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template<typename PointerType, typename std::enable_if<
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std::is_pointer<PointerType>::value, int>::type = 0>
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auto get_ptr() noexcept -> decltype(std::declval<basic_json_t&>().get_impl_ptr(std::declval<PointerType>()))
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{
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return *this;
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// delegate the call to get_impl_ptr<>()
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return get_impl_ptr(static_cast<PointerType>(nullptr));
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}
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/*!
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@brief get special-case overload
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This overloads converts the current @ref basic_json in a different
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@ref basic_json type
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@tparam BasicJsonType == @ref basic_json
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@return a copy of *this, converted into @tparam BasicJsonType
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@complexity Depending on the implementation of the called `from_json()`
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method.
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@since version 3.2.0
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@brief get a pointer value (implicit)
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@copydoc get_ptr()
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*/
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template < typename BasicJsonType, detail::enable_if_t <
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!std::is_same<BasicJsonType, basic_json>::value&&
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detail::is_basic_json<BasicJsonType>::value, int > = 0 >
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BasicJsonType get() const
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template < typename PointerType, typename std::enable_if <
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std::is_pointer<PointerType>::value&&
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std::is_const<typename std::remove_pointer<PointerType>::type>::value, int >::type = 0 >
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constexpr auto get_ptr() const noexcept -> decltype(std::declval<const basic_json_t&>().get_impl_ptr(std::declval<PointerType>()))
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{
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return *this;
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// delegate the call to get_impl_ptr<>() const
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return get_impl_ptr(static_cast<PointerType>(nullptr));
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}
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private:
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/*!
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@brief get a value (explicit)
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@ -2923,21 +2926,12 @@ class basic_json
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*/
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template < typename ValueTypeCV, typename ValueType = detail::uncvref_t<ValueTypeCV>,
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detail::enable_if_t <
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!detail::is_basic_json<ValueType>::value &&
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detail::has_from_json<basic_json_t, ValueType>::value &&
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!detail::has_non_default_from_json<basic_json_t, ValueType>::value,
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detail::is_default_constructible<ValueType>::value &&
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detail::has_from_json<basic_json_t, ValueType>::value,
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int > = 0 >
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ValueType get() const noexcept(noexcept(
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JSONSerializer<ValueType>::from_json(std::declval<const basic_json_t&>(), std::declval<ValueType&>())))
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ValueType get_impl(detail::priority_tag<0> /*unused*/) const noexcept(noexcept(
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JSONSerializer<ValueType>::from_json(std::declval<const basic_json_t&>(), std::declval<ValueType&>())))
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{
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// we cannot static_assert on ValueTypeCV being non-const, because
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// there is support for get<const basic_json_t>(), which is why we
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// still need the uncvref
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static_assert(!std::is_reference<ValueTypeCV>::value,
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"get() cannot be used with reference types, you might want to use get_ref()");
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static_assert(std::is_default_constructible<ValueType>::value,
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"types must be DefaultConstructible when used with get()");
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ValueType ret;
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JSONSerializer<ValueType>::from_json(*this, ret);
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return ret;
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@ -2975,15 +2969,142 @@ class basic_json
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@since version 2.1.0
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*/
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template < typename ValueTypeCV, typename ValueType = detail::uncvref_t<ValueTypeCV>,
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detail::enable_if_t < !std::is_same<basic_json_t, ValueType>::value &&
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detail::has_non_default_from_json<basic_json_t, ValueType>::value,
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int > = 0 >
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ValueType get() const noexcept(noexcept(
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JSONSerializer<ValueType>::from_json(std::declval<const basic_json_t&>())))
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detail::enable_if_t <
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detail::has_non_default_from_json<basic_json_t, ValueType>::value,
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int > = 0 >
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ValueType get_impl(detail::priority_tag<1> /*unused*/) const noexcept(noexcept(
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JSONSerializer<ValueType>::from_json(std::declval<const basic_json_t&>())))
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{
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return JSONSerializer<ValueType>::from_json(*this);
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}
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/*!
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@brief get special-case overload
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This overloads converts the current @ref basic_json in a different
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@ref basic_json type
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@tparam BasicJsonType == @ref basic_json
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@return a copy of *this, converted into @tparam BasicJsonType
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@complexity Depending on the implementation of the called `from_json()`
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method.
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@since version 3.2.0
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*/
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template < typename BasicJsonType, detail::enable_if_t <
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detail::is_basic_json<BasicJsonType>::value,
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int > = 0 >
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BasicJsonType get_impl(detail::priority_tag<2> /*unused*/) const
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{
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return *this;
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}
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/*!
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@brief get special-case overload
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This overloads avoids a lot of template boilerplate, it can be seen as the
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identity method
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@tparam BasicJsonType == @ref basic_json
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@return a copy of *this
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@complexity Constant.
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@since version 2.1.0
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*/
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template<typename BasicJsonType, detail::enable_if_t<
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std::is_same<BasicJsonType, basic_json_t>::value,
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int> = 0>
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basic_json get_impl(detail::priority_tag<3> /*unused*/) const
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{
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return *this;
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}
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/*!
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@brief get a pointer value (explicit)
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@copydoc get()
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*/
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template<typename PointerType, detail::enable_if_t<
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std::is_pointer<PointerType>::value, int> = 0>
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constexpr auto get_impl(detail::priority_tag<4> /*unused*/) const noexcept
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-> decltype(std::declval<const basic_json_t&>().template get_ptr<PointerType>())
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{
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// delegate the call to get_ptr
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return get_ptr<PointerType>();
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}
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public:
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/*!
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@brief get a (pointer) value (explicit)
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Performs explicit type conversion between the JSON value and a compatible value if required.
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- If the requested type is a pointer to the internally stored JSON value that pointer is returned.
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No copies are made.
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- If the requested type is the current @ref basic_json, or a different @ref basic_json convertible
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from the current @ref basic_json.
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- Otherwise the value is converted by calling the @ref json_serializer<ValueType> `from_json()`
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method.
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@tparam ValueTypeCV the provided value type
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@tparam ValueType the returned value type
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@return copy of the JSON value, converted to @tparam ValueType if necessary
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@throw what @ref json_serializer<ValueType> `from_json()` method throws if conversion is required
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@since version 2.1.0
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*/
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template < typename ValueTypeCV, typename ValueType = detail::uncvref_t<ValueTypeCV>>
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constexpr auto get() const noexcept(noexcept(get_impl<ValueType>(detail::priority_tag<4> {})))
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-> decltype(get_impl<ValueType>(detail::priority_tag<4> {}))
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{
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// we cannot static_assert on ValueTypeCV being non-const, because
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// there is support for get<const basic_json_t>(), which is why we
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// still need the uncvref
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static_assert(!std::is_reference<ValueTypeCV>::value,
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"get() cannot be used with reference types, you might want to use get_ref()");
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return JSONSerializer<ValueType>::from_json(*this);
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return get_impl<ValueType>(detail::priority_tag<4> {});
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}
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/*!
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@brief get a pointer value (explicit)
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Explicit pointer access to the internally stored JSON value. No copies are
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made.
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@warning The pointer becomes invalid if the underlying JSON object
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changes.
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@tparam PointerType pointer type; must be a pointer to @ref array_t, @ref
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object_t, @ref string_t, @ref boolean_t, @ref number_integer_t,
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@ref number_unsigned_t, or @ref number_float_t.
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@return pointer to the internally stored JSON value if the requested
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pointer type @a PointerType fits to the JSON value; `nullptr` otherwise
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@complexity Constant.
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@liveexample{The example below shows how pointers to internal values of a
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JSON value can be requested. Note that no type conversions are made and a
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`nullptr` is returned if the value and the requested pointer type does not
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match.,get__PointerType}
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@sa @ref get_ptr() for explicit pointer-member access
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@since version 1.0.0
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*/
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template<typename PointerType, typename std::enable_if<
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std::is_pointer<PointerType>::value, int>::type = 0>
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auto get() noexcept -> decltype(std::declval<basic_json_t&>().template get_ptr<PointerType>())
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{
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// delegate the call to get_ptr
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return get_ptr<PointerType>();
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}
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/*!
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@ -3056,101 +3177,6 @@ class basic_json
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return v;
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}
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/*!
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@brief get a pointer value (implicit)
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Implicit pointer access to the internally stored JSON value. No copies are
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made.
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@warning Writing data to the pointee of the result yields an undefined
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state.
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@tparam PointerType pointer type; must be a pointer to @ref array_t, @ref
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object_t, @ref string_t, @ref boolean_t, @ref number_integer_t,
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@ref number_unsigned_t, or @ref number_float_t. Enforced by a static
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assertion.
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@return pointer to the internally stored JSON value if the requested
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pointer type @a PointerType fits to the JSON value; `nullptr` otherwise
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@complexity Constant.
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@liveexample{The example below shows how pointers to internal values of a
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JSON value can be requested. Note that no type conversions are made and a
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`nullptr` is returned if the value and the requested pointer type does not
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match.,get_ptr}
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@since version 1.0.0
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*/
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template<typename PointerType, typename std::enable_if<
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std::is_pointer<PointerType>::value, int>::type = 0>
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auto get_ptr() noexcept -> decltype(std::declval<basic_json_t&>().get_impl_ptr(std::declval<PointerType>()))
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{
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// delegate the call to get_impl_ptr<>()
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return get_impl_ptr(static_cast<PointerType>(nullptr));
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}
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/*!
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@brief get a pointer value (implicit)
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@copydoc get_ptr()
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*/
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template < typename PointerType, typename std::enable_if <
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std::is_pointer<PointerType>::value&&
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std::is_const<typename std::remove_pointer<PointerType>::type>::value, int >::type = 0 >
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constexpr auto get_ptr() const noexcept -> decltype(std::declval<const basic_json_t&>().get_impl_ptr(std::declval<PointerType>()))
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{
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// delegate the call to get_impl_ptr<>() const
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return get_impl_ptr(static_cast<PointerType>(nullptr));
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}
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/*!
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@brief get a pointer value (explicit)
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Explicit pointer access to the internally stored JSON value. No copies are
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made.
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@warning The pointer becomes invalid if the underlying JSON object
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changes.
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@tparam PointerType pointer type; must be a pointer to @ref array_t, @ref
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object_t, @ref string_t, @ref boolean_t, @ref number_integer_t,
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@ref number_unsigned_t, or @ref number_float_t.
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@return pointer to the internally stored JSON value if the requested
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pointer type @a PointerType fits to the JSON value; `nullptr` otherwise
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@complexity Constant.
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@liveexample{The example below shows how pointers to internal values of a
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JSON value can be requested. Note that no type conversions are made and a
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`nullptr` is returned if the value and the requested pointer type does not
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match.,get__PointerType}
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@sa @ref get_ptr() for explicit pointer-member access
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@since version 1.0.0
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*/
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template<typename PointerType, typename std::enable_if<
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std::is_pointer<PointerType>::value, int>::type = 0>
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auto get() noexcept -> decltype(std::declval<basic_json_t&>().template get_ptr<PointerType>())
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{
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// delegate the call to get_ptr
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return get_ptr<PointerType>();
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}
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/*!
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@brief get a pointer value (explicit)
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@copydoc get()
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*/
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template<typename PointerType, typename std::enable_if<
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std::is_pointer<PointerType>::value, int>::type = 0>
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constexpr auto get() const noexcept -> decltype(std::declval<const basic_json_t&>().template get_ptr<PointerType>())
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{
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// delegate the call to get_ptr
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return get_ptr<PointerType>();
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}
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/*!
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@brief get a reference value (implicit)
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