Github   Telegram
Loading...
Searching...
No Matches
value_builder.hpp
Go to the documentation of this file.
1#pragma once
2
3/// @file userver/formats/json/value_builder.hpp
4/// @brief @copybrief formats::json::ValueBuilder
5
6#include <chrono>
7#include <string_view>
8#include <vector>
9
10#include <userver/formats/common/meta.hpp>
11#include <userver/formats/common/transfer_tag.hpp>
12#include <userver/formats/json/impl/mutable_value_wrapper.hpp>
13#include <userver/formats/json/value.hpp>
14#include <userver/utils/strong_typedef.hpp>
15
16USERVER_NAMESPACE_BEGIN
17
18namespace formats::json {
19
20// clang-format off
21
22/// @ingroup userver_containers userver_formats
23///
24/// @brief Builder for JSON.
25///
26/// Class provides methods for building JSON. For read only access to the
27/// existing JSON values use formats::json::Value.
28///
29/// ## Example usage:
30///
31/// @snippet formats/json/value_builder_test.cpp Sample formats::json::ValueBuilder usage
32///
33/// ## Customization example:
34///
35/// @snippet formats/json/value_builder_test.cpp Sample Customization formats::json::ValueBuilder usage
36///
37/// @see @ref md_en_userver_formats
38
39// clang-format on
40
41class ValueBuilder final {
42 public:
43 struct IterTraits {
44 using ValueType = formats::json::ValueBuilder;
45 using Reference = formats::json::ValueBuilder&;
46 using Pointer = formats::json::ValueBuilder*;
47 using ContainerType = impl::MutableValueWrapper;
48 };
49
50 using iterator = Iterator<IterTraits>;
51
52 /// Constructs a ValueBuilder that holds kNull
53 ValueBuilder() noexcept = default;
54
55 /// Constructs a valueBuilder that holds default value for provided `type`.
57
58 /// @brief Transfers the `ValueBuilder` object
59 /// @see formats::common::TransferTag for the transfer semantics
60 ValueBuilder(common::TransferTag, ValueBuilder&&) noexcept;
61
62 ValueBuilder(const ValueBuilder& other);
63 // NOLINTNEXTLINE(performance-noexcept-move-constructor)
64 ValueBuilder(ValueBuilder&& other);
65 ValueBuilder& operator=(const ValueBuilder& other);
66 // NOLINTNEXTLINE(performance-noexcept-move-constructor)
67 ValueBuilder& operator=(ValueBuilder&& other);
68
69 ValueBuilder(const formats::json::Value& other);
70 ValueBuilder(formats::json::Value&& other);
71
72 /// Converting constructors.
73 ValueBuilder(bool t);
74 ValueBuilder(const char* str);
75 ValueBuilder(const std::string& str);
76 ValueBuilder(std::string_view str);
77 ValueBuilder(int t);
78 ValueBuilder(unsigned int t);
79 ValueBuilder(uint64_t t);
80 ValueBuilder(int64_t t);
81 ValueBuilder(float t);
82 ValueBuilder(double t);
83
84 /// Universal constructor using Serialize
85 template <typename T>
86 ValueBuilder(const T& t) : ValueBuilder(DoSerialize(t)) {}
87
88 /// @brief Access member by key for modification.
89 /// @throw `TypeMismatchException` if not object or null value.
90 ValueBuilder operator[](std::string key);
91 /// @brief Access array member by index for modification.
92 /// @throw `TypeMismatchException` if not an array value.
93 /// @throw `OutOfBoundsException` if index is greater than size.
94 ValueBuilder operator[](std::size_t index);
95 /// @brief Access member by key for modification.
96 /// @throw `TypeMismatchException` if not object or null value.
97 template <
98 typename Tag, utils::StrongTypedefOps Ops,
99 typename Enable = std::enable_if_t<utils::IsStrongTypedefLoggable(Ops)>>
100 ValueBuilder operator[](utils::StrongTypedef<Tag, std::string, Ops> key);
101
102 /// @brief Emplaces new member w/o a check whether the key already exists.
103 /// @warning May create invalid JSON with duplicate key.
104 /// @throw `TypeMismatchException` if not object or null value.
105 void EmplaceNocheck(const std::string& key, ValueBuilder value);
106
107 /// @brief Remove key from object. If key is missing nothing happens.
108 /// @throw `TypeMismatchException` if value is not an object.
109 void Remove(const std::string& key);
110
111 iterator begin();
112 iterator end();
113
114 /// @brief Returns whether the array or object is empty.
115 /// @throw `TypeMismatchException` if not an array or an object.
116 bool IsEmpty() const;
117
118 /// @brief Returns true if *this holds a Null (Type::kNull).
119 bool IsNull() const noexcept;
120
121 /// @brief Returns true if *this is convertible to bool.
122 bool IsBool() const noexcept;
123
124 /// @brief Returns true if *this is convertible to int.
125 bool IsInt() const noexcept;
126
127 /// @brief Returns true if *this is convertible to int64_t.
128 bool IsInt64() const noexcept;
129
130 /// @brief Returns true if *this is convertible to uint64_t.
131 bool IsUInt64() const noexcept;
132
133 /// @brief Returns true if *this is convertible to double.
134 bool IsDouble() const noexcept;
135
136 /// @brief Returns true if *this is convertible to std::string.
137 bool IsString() const noexcept;
138
139 /// @brief Returns true if *this is an array (Type::kArray).
140 bool IsArray() const noexcept;
141
142 /// @brief Returns true if *this holds a map (Type::kObject).
143 bool IsObject() const noexcept;
144
145 /// @brief Returns array size or object members count.
146 /// @throw `TypeMismatchException` if not an array or an object.
147 std::size_t GetSize() const;
148
149 /// @brief Returns true if value holds a `key`.
150 /// @throw `TypeMismatchException` if not an object or null.
151 bool HasMember(const char* key) const;
152
153 /// @brief Returns true if value holds a `key`.
154 /// @throw `TypeMismatchException` if `*this` is not a map or null.
155 bool HasMember(const std::string& key) const;
156
157 /// @brief Returns full path to this value.
158 std::string GetPath() const;
159
160 /// @brief Resize the array value or convert null value
161 /// into an array of requested size.
162 /// @throw `TypeMismatchException` if not an array or null.
163 void Resize(std::size_t size);
164
165 /// @brief Add element into the last position of array.
166 /// @throw `TypeMismatchException` if not an array or null.
167 void PushBack(ValueBuilder&& bld);
168
169 /// @brief Take out the resulting `Value` object.
170 /// After calling this method the object is in unspecified
171 /// (but valid - possibly null) state.
172 /// @throw `JsonException` if called not from the root builder.
173 formats::json::Value ExtractValue();
174
175 private:
176 class EmplaceEnabler {};
177
178 public:
179 /// @cond
180 ValueBuilder(EmplaceEnabler, impl::MutableValueWrapper) noexcept;
181 /// @endcond
182
183 private:
184 enum class CheckMemberExists { kYes, kNo };
185
186 explicit ValueBuilder(impl::MutableValueWrapper) noexcept;
187
188 static void Copy(impl::Value& to, const ValueBuilder& from);
189 static void Move(impl::Value& to, ValueBuilder&& from);
190
191 impl::Value& AddMember(const std::string& key, CheckMemberExists);
192
193 template <typename T>
194 static Value DoSerialize(const T& t);
195
196 impl::MutableValueWrapper value_;
197
198 friend class Iterator<IterTraits, common::IteratorDirection::kForward>;
199 friend class Iterator<IterTraits, common::IteratorDirection::kReverse>;
200};
201
202template <typename T>
203Value ValueBuilder::DoSerialize(const T& t) {
204 static_assert(
205 formats::common::impl::kHasSerialize<Value, T>,
206 "There is no `Serialize(const T&, formats::serialize::To<json::Value>)` "
207 "in namespace of `T` or `formats::serizalize`. "
208 ""
209 "Probably you forgot to include the "
210 "<userver/formats/serialize/common_containers.hpp> header "
211 "or one of the <formats/json/serialize_*.hpp> headers or you "
212 "have not provided a `Serialize` function overload.");
213
214 return Serialize(t, formats::serialize::To<Value>());
215}
216
217template <typename T>
218std::enable_if_t<std::is_integral<T>::value && sizeof(T) <= sizeof(int64_t),
219 Value>
220Serialize(T value, formats::serialize::To<Value>) {
221 using Type = std::conditional_t<std::is_signed<T>::value, int64_t, uint64_t>;
222 return json::ValueBuilder(static_cast<Type>(value)).ExtractValue();
223}
224
225json::Value Serialize(std::chrono::system_clock::time_point tp,
226 formats::serialize::To<Value>);
227
228template <typename Tag, utils::StrongTypedefOps Ops, typename Enable>
229ValueBuilder ValueBuilder::operator[](
230 utils::StrongTypedef<Tag, std::string, Ops> key) {
231 return (*this)[std::move(key.GetUnderlying())];
232}
233
234} // namespace formats::json
235
236USERVER_NAMESPACE_END