formats::json::ValueBuilder Class Reference

Builder for JSON. More...

#include <userver/formats/json/value_builder.hpp>

Classes
struct	IterTraits

Public Types
using	iterator = Iterator< IterTraits >

Public Member Functions
	ValueBuilder () noexcept=default
	Constructs a ValueBuilder that holds kNull.
	ValueBuilder (Type type)
	Constructs a valueBuilder that holds default value for provided type.
	ValueBuilder (common::TransferTag, ValueBuilder &&) noexcept
	Transfers the ValueBuilder object. More...
	ValueBuilder (const ValueBuilder &other)
	ValueBuilder (ValueBuilder &&other)
ValueBuilder &	operator= (const ValueBuilder &other)
ValueBuilder &	operator= (ValueBuilder &&other)
	ValueBuilder (const formats::json::Value &other)
	ValueBuilder (formats::json::Value &&other)
	ValueBuilder (bool t)
	Converting constructors.
	ValueBuilder (const char *str)
	ValueBuilder (const std::string &str)
	ValueBuilder (std::string_view str)
	ValueBuilder (int t)
	ValueBuilder (unsigned int t)
	ValueBuilder (uint64_t t)
	ValueBuilder (int64_t t)
	ValueBuilder (float t)
	ValueBuilder (double t)
template<typename T >
	ValueBuilder (const T &t)
	Universal constructor using Serialize. More...
ValueBuilder	operator[] (std::string key)
	Access member by key for modification. More...
ValueBuilder	operator[] (std::size_t index)
	Access array member by index for modification. More...
template<typename Tag , utils::StrongTypedefOps Ops, typename Enable = std::enable_if_t<utils::IsStrongTypedefLoggable(Ops)>>
ValueBuilder	operator[] (utils::StrongTypedef< Tag, std::string, Ops > key)
	Access member by key for modification. More...
void	EmplaceNocheck (const std::string &key, ValueBuilder value)
	Emplaces new member w/o a check whether the key already exists. More...
void	Remove (const std::string &key)
	Remove key from object. If key is missing nothing happens. More...
iterator	begin ()
iterator	end ()
bool	IsEmpty () const
	Returns whether the array or object is empty. More...
bool	IsNull () const noexcept
	Returns true if *this holds a Null (Type::kNull).
bool	IsBool () const noexcept
	Returns true if *this is convertible to bool.
bool	IsInt () const noexcept
	Returns true if *this is convertible to int.
bool	IsInt64 () const noexcept
	Returns true if *this is convertible to int64_t.
bool	IsUInt64 () const noexcept
	Returns true if *this is convertible to uint64_t.
bool	IsDouble () const noexcept
	Returns true if *this is convertible to double.
bool	IsString () const noexcept
	Returns true if *this is convertible to std::string.
bool	IsArray () const noexcept
	Returns true if *this is an array (Type::kArray).
bool	IsObject () const noexcept
	Returns true if *this holds a map (Type::kObject).
std::size_t	GetSize () const
	Returns array size or object members count. More...
bool	HasMember (const char *key) const
	Returns true if value holds a key. More...
bool	HasMember (const std::string &key) const
	Returns true if value holds a key. More...
std::string	GetPath () const
	Returns full path to this value.
void	Resize (std::size_t size)
	Resize the array value or convert null value into an array of requested size. More...
void	PushBack (ValueBuilder &&bld)
	Add element into the last position of array. More...
formats::json::Value	ExtractValue ()
	Take out the resulting Value object. After calling this method the object is in unspecified (but valid - possibly null) state. More...

Friends
class	Iterator< IterTraits, common::IteratorDirection::kForward >
class	Iterator< IterTraits, common::IteratorDirection::kReverse >

Detailed Description

Builder for JSON.

Class provides methods for building JSON. For read only access to the existing JSON values use formats::json::Value.

Example usage:

  // #include <userver/formats/json.hpp>
  formats::json::ValueBuilder builder;
  builder["key1"] = 1;
  builder["key2"]["key3"] = "val";
  formats::json::Value json = builder.ExtractValue();
 
  ASSERT_EQ(json["key1"].As<int>(), 1);
  ASSERT_EQ(json["key2"]["key3"].As<std::string>(), "val");

Customization example:

namespace my_namespace {
 
struct MyKeyValue {
  std::string field1;
  int field2;
};
 
// The function must be declared in the namespace of your type
formats::json::Value Serialize(const MyKeyValue& data,
                               formats::serialize::To<formats::json::Value>) {
  formats::json::ValueBuilder builder;
  builder["field1"] = data.field1;
  builder["field2"] = data.field2;
 
  return builder.ExtractValue();
}
 
TEST(JsonValueBuilder, ExampleCustomization) {
  MyKeyValue object = {"val", 1};
  formats::json::ValueBuilder builder;
  builder["example"] = object;
  auto json = builder.ExtractValue();
  ASSERT_EQ(json["example"]["field1"].As<std::string>(), "val");
  ASSERT_EQ(json["example"]["field2"].As<int>(), 1);
}
 
}  // namespace my_namespace
 

See also

Formats (JSON, YAML, BSON, ...)

Examples

samples/config_service/config_service.cpp, samples/mongo_service/mongo_service.cpp, samples/tcp_full_duplex_service/tcp_full_duplex_service.cpp, samples/testsuite-support/src/metrics.cpp, samples/testsuite-support/src/now.cpp, and samples/testsuite-support/src/testpoint.cpp.

Definition at line 41 of file value_builder.hpp.

Member Typedef Documentation

iterator

using formats::json::ValueBuilder::iterator = Iterator<IterTraits>

Definition at line 50 of file value_builder.hpp.

Constructor & Destructor Documentation

ValueBuilder() [1/2]

formats::json::ValueBuilder::ValueBuilder ( common::TransferTag  , ValueBuilder &&    )

noexcept

Transfers the ValueBuilder object.

See also

formats::common::TransferTag for the transfer semantics

ValueBuilder() [2/2]

template<typename T >

formats::json::ValueBuilder::ValueBuilder ( const T &  t )

inline

Universal constructor using Serialize.

Definition at line 86 of file value_builder.hpp.

Member Function Documentation

EmplaceNocheck()

void formats::json::ValueBuilder::EmplaceNocheck	(	const std::string &	key,
		ValueBuilder	value
	)

Emplaces new member w/o a check whether the key already exists.

Warning

May create invalid JSON with duplicate key.

Exceptions

`TypeMismatchException`

if not object or null value.

ExtractValue()

formats::json::Value formats::json::ValueBuilder::ExtractValue

(

)

Take out the resulting Value object. After calling this method the object is in unspecified (but valid - possibly null) state.

Exceptions

`JsonException`

if called not from the root builder.

Examples

samples/config_service/config_service.cpp, samples/mongo_service/mongo_service.cpp, samples/tcp_full_duplex_service/tcp_full_duplex_service.cpp, samples/testsuite-support/src/metrics.cpp, samples/testsuite-support/src/now.cpp, and samples/testsuite-support/src/testpoint.cpp.

GetSize()

std::size_t formats::json::ValueBuilder::GetSize

(

)

const

Returns array size or object members count.

Exceptions

`TypeMismatchException`

if not an array or an object.

HasMember() [1/2]

bool formats::json::ValueBuilder::HasMember

(

const char *

key

)

const

Returns true if value holds a key.

Exceptions

`TypeMismatchException`

if not an object or null.

HasMember() [2/2]

bool formats::json::ValueBuilder::HasMember

(

const std::string &

key

)

const

Returns true if value holds a key.

Exceptions

`TypeMismatchException`

if *this is not a map or null.

IsEmpty()

bool formats::json::ValueBuilder::IsEmpty

(

)

const

Returns whether the array or object is empty.

Exceptions

`TypeMismatchException`

if not an array or an object.

operator[]() [1/3]

ValueBuilder formats::json::ValueBuilder::operator[]

(

std::size_t

index

)

Access array member by index for modification.

Exceptions

`TypeMismatchException`	if not an array value.
`OutOfBoundsException`	if index is greater than size.

operator[]() [2/3]

ValueBuilder formats::json::ValueBuilder::operator[]

(

std::string

key

)

Access member by key for modification.

Exceptions

`TypeMismatchException`

if not object or null value.

operator[]() [3/3]

template<typename Tag , utils::StrongTypedefOps Ops, typename Enable = std::enable_if_t<utils::IsStrongTypedefLoggable(Ops)>>

ValueBuilder formats::json::ValueBuilder::operator[]

(

utils::StrongTypedef< Tag, std::string, Ops >

key

)

Access member by key for modification.

Exceptions

`TypeMismatchException`

if not object or null value.

PushBack()

void formats::json::ValueBuilder::PushBack

(

ValueBuilder &&

bld

)

Add element into the last position of array.

Exceptions

`TypeMismatchException`

if not an array or null.

Remove()

void formats::json::ValueBuilder::Remove

(

const std::string &

key

)

Remove key from object. If key is missing nothing happens.

Exceptions

`TypeMismatchException`

if value is not an object.

Resize()

void formats::json::ValueBuilder::Resize

(

std::size_t

size

)

Resize the array value or convert null value into an array of requested size.

Exceptions

`TypeMismatchException`

if not an array or null.

Friends And Related Function Documentation

Iterator< IterTraits, common::IteratorDirection::kForward >

friend class Iterator< IterTraits, common::IteratorDirection::kForward >

friend

Definition at line 196 of file value_builder.hpp.

Iterator< IterTraits, common::IteratorDirection::kReverse >

friend class Iterator< IterTraits, common::IteratorDirection::kReverse >

friend

Definition at line 196 of file value_builder.hpp.

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The documentation for this class was generated from the following file:

• userver/formats/json/value_builder.hpp