BT::JsonExporter Class Reference

#include <json_export.h>

Public Types
using	Entry = std::pair< BT::Any, BT::TypeInfo >
	This information is needed to create a BT::Blackboard::entry.
using	ExpectedEntry = nonstd::expected< Entry, std::string >

Public Member Functions
	JsonExporter (const JsonExporter &)=delete
JsonExporter &	operator= (const JsonExporter &)=delete
	JsonExporter (JsonExporter &&)=delete
JsonExporter &	operator= (JsonExporter &&)=delete
bool	toJson (const BT::Any &any, nlohmann::json &destination) const
	toJson adds the content of "any" to the JSON "destination".
ExpectedEntry	fromJson (const nlohmann::json &source) const
	fromJson will return an Entry (value wrappedn in Any + TypeInfo) from a json source. If it is a custom type, you might register it first with addConverter().
ExpectedEntry	fromJson (const nlohmann::json &source, std::type_index type) const
template<typename T >
Expected< T >	fromJson (const nlohmann::json &source) const
template<typename T >
void	addConverter ()
	Register new JSON converters with addConverter<Foo>(). You should used first the macro BT_JSON_CONVERTER. The conversions from/to vector<T> are automatically registered.
template<typename T >
void	addConverter (std::function< void(const T &, nlohmann::json &)> to_json, bool add_type=true)
	addConverter register a to_json function that converts a json to a type T. The conversion to std:vector<T> is automatically registered.
template<typename T >
void	addConverter (std::function< void(const nlohmann::json &, T &)> from_json)
	addConverter register a from_json function that converts a json to a type T. The conversions from std::vector<T> is automatically registered.

Static Public Member Functions
static JsonExporter &	get ()

Detailed Description

To add new type to the JSON library, you should follow these instructions: https://json.nlohmann.me/features/arbitrary_types/

Considering for instance the type:

struct Point2D { double x; double y; };

This would require the implementation of:

void to_json(nlohmann::json& j, const Point2D& point); void from_json(const nlohmann::json& j, Point2D& point);

To avoid repeating yourself, we provide the macro BT_JSON_CONVERTION that implements both those function, at once. Usage:

BT_JSON_CONVERTER(Point2D, point) { add_field("x", &point.x); add_field("y", &point.y); }

Later, you MUST register the type using:

BT::RegisterJsonDefinition<Point2D>(); Use RegisterJsonDefinition<Foo>();

Member Function Documentation

addConverter() [1/2]

template<typename T >

void BT::JsonExporter::addConverter ( std::function< void(const nlohmann::json &, T &)>  from_json )

inline

addConverter register a from_json function that converts a json to a type T. The conversions from std::vector<T> is automatically registered.

Parameters

from_json

the function with signature void(const nlohmann::json&, T&)

addConverter() [2/2]

template<typename T >

void BT::JsonExporter::addConverter ( std::function< void(const T &, nlohmann::json &)>  to_json, bool  add_type = true  )

inline

addConverter register a to_json function that converts a json to a type T. The conversion to std:vector<T> is automatically registered.

Parameters

to_json	the function with signature void(const T&, nlohmann::json&)
add_type	if true, add a field called [__type] with the name of the type.

fromJson() [1/2]

ExpectedEntry BT::JsonExporter::fromJson

(

const nlohmann::json &

source

)

const

fromJson will return an Entry (value wrappedn in Any + TypeInfo) from a json source. If it is a custom type, you might register it first with addConverter().

Parameters

source

Returns

fromJson() [2/2]

ExpectedEntry BT::JsonExporter::fromJson	(	const nlohmann::json &	source,
		std::type_index	type
	)		const

Same as the other, but providing the specific type, To be preferred if the JSON doesn't contain the field [__type]

toJson()

bool BT::JsonExporter::toJson	(	const BT::Any &	any,
		nlohmann::json &	destination
	)		const

toJson adds the content of "any" to the JSON "destination".

It will return false if the conversion toJson is not possible If it is a custom type, you might register it first with addConverter().

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

• include/behaviortree_cpp/json_export.h