#include <types.hpp>

Inheritance diagram for opcua::Variant:

Detailed Description

UA_Variant wrapper class.

Variants may contain scalar values or arrays of any type together with a type definition. The standard mandates that variants contain built-in data types only. open62541 transparently handles this wrapping in the encoding layer. If the type is unknown to the receiver, the variant stores the original ExtensionObject in binary or XML encoding.

open62541pp enhances variant handling with the following features:

Type category detection: Identifies whether T is scalar or array:
- Scalar, if T is:
  - A registered type (TypeRegistry spezialization). This applies to native types and wrapper types.
  - A convertible type (TypeConverter spezialization).
- Array, if T is a container type (e.g. std::vector or std::list) and does not satisfy the criterias of a scalar type.
Applied in constructors, assign, and to functions:

opcua::Variant var{5}; // set scalar (via constructor)

auto value = var.to<int>(); // convert scalar

std::array<int> array{1, 2, 3};

var.assign(array); // set array (via assign)

auto vec = var.to<std::vector<int>>(); // convert array

opcua::Variant
UA_Variant wrapper class.
Definition types.hpp:1048

opcua::Variant::to
T to() const &
Converts the variant to the specified type T with automatic conversion if required.
Definition types.hpp:1374

opcua::Variant::array
Span< T > array()
Get array with given template type (only native or wrapper types).
Definition types.hpp:1338
Type definition retrieval: Automatically retrieves UA_DataType via TypeRegistry. For every registered type T, the type definition parameter can be omitted:

opcua::Variant var{5, UA_TYPES[UA_TYPES_INT]}; // explicit type definition

opcua::Variant var{5}; // auto-detected type definition

UA_TYPES
const UA_DataType UA_TYPES[191]
Type conversion: Convert non-native types using TypeConverter. Native UA_* types can be assigned and retrieved to/from variants without any conversion, because their binary layout is described by the type definition (UA_DataType). The same is true for wrapper types, that share the exact memory layout as their wrapped native type. Non-native types, like std::string from the STL, may not be describeable by UA_DataType because their memory layout is an implementation detail. Instead, the conversion between non-native and native types can be defined with template specializations of TypeConverter. If a type is convertible (TypeConverter specialization), the Variant automatically manages the conversion, requiring a copy:

opcua::Variant var{std::string{"test"}}; // convert to native type (copy)

auto& native = var.scalar<opcua::String>(); // reference to native type (no copy)

auto str = var.to<std::string>(); // conversion (copy required)

opcua::String
UA_String wrapper class.
Definition types.hpp:256

opcua::Variant::scalar
T & scalar() &
Get scalar value with given template type (only native or wrapper types).
Definition types.hpp:1311

opcua::Wrapper::native
constexpr const T & native() const noexcept
Definition wrapper.hpp:243

Examples: custom_datatypes/client_custom_datatypes.cpp, custom_datatypes/server_custom_datatypes.cpp, method/client_method_async.cpp, server.cpp, server_accesscontrol.cpp, server_datasource.cpp, server_instantiation.cpp, server_minimal.cpp, server_valuecallback.cpp, and typeconversion.cpp.

Definition at line 1048 of file types.hpp.

Public Member Functions
template<typename T , typename = std::enable_if_t<!std::is_const_v<T>>>
	Variant (T *ptr) noexcept

template<typename T , typename = std::enable_if_t<!std::is_const_v<T>>>
	Variant (T *ptr, const UA_DataType &type) noexcept

template<typename T , typename = std::enable_if_t<!isVariant<T>>>
	Variant (T &&value)

template<typename T >
	Variant (T &&value, const UA_DataType &type)

template<typename InputIt >
	Variant (InputIt first, InputIt last)

template<typename InputIt >
	Variant (InputIt first, InputIt last, const UA_DataType &type)

constexpr	Wrapper () noexcept=default

constexpr	Wrapper (const Wrapper &other)

constexpr	Wrapper (const T &native)

constexpr	Wrapper (Wrapper &&other) noexcept

constexpr	Wrapper (T &&native) noexcept

Modifiers
Modify internal scalar/array value.
void	assign (std::nullptr_t ptr) noexcept=delete

void	assign (std::nullptr_t ptr, const UA_DataType &type) noexcept=delete

template<typename T , typename = std::enable_if_t<!std::is_const_v<T>>>
void	assign (T *ptr) noexcept

template<typename T , typename = std::enable_if_t<!std::is_const_v<T>>>
void	assign (T *ptr, const UA_DataType &type) noexcept

template<typename T >
void	assign (T &&value)

template<typename T >
void	assign (T &&value, const UA_DataType &type)

template<typename InputIt >
void	assign (InputIt first, InputIt last)

template<typename InputIt >
void	assign (InputIt first, InputIt last, const UA_DataType &type)

template<typename T , typename = std::enable_if_t<!isVariant<T>>>
Variant &	operator= (T *value) noexcept

template<typename T , typename = std::enable_if_t<!isVariant<T>>>
Variant &	operator= (T &&value)

Observers
Check the type category, type definition and array structure of the internal value.
bool	empty () const noexcept

bool	isScalar () const noexcept

bool	isArray () const noexcept

bool	isType (const UA_DataType *type) const noexcept

bool	isType (const UA_DataType &type) const noexcept

bool	isType (const NodeId &id) const noexcept

template<typename T >
bool	isType () const noexcept

const UA_DataType *	type () const noexcept

size_t	arrayLength () const noexcept

Span< const uint32_t >	arrayDimensions () const noexcept

Accessors
Access and convert internal scalar/array value.
void *	data () noexcept

const void *	data () const noexcept

template<typename T >
T &	scalar () &

template<typename T >
const T &	scalar () const &

template<typename T >
T	scalar () &&

template<typename T >
T	scalar () const &&

template<typename T >
Span< T >	array ()

template<typename T >
Span< const T >	array () const

template<typename T >
T	to () const &

template<typename T >
T	to () &&

Public Member Functions inherited from opcua::Wrapper< T, Handler >
constexpr	Wrapper () noexcept=default

constexpr	Wrapper (const Wrapper &other)

constexpr	Wrapper (const T &native)

constexpr	Wrapper (Wrapper &&other) noexcept

constexpr	Wrapper (T &&native) noexcept

	~Wrapper () noexcept=default

constexpr Wrapper &	operator= (const Wrapper &other)

constexpr Wrapper &	operator= (const T &native)

constexpr Wrapper &	operator= (Wrapper &&other) noexcept

constexpr Wrapper &	operator= (T &&native) noexcept

constexpr	operator T& () noexcept

constexpr	operator const T & () const noexcept

constexpr T *	operator-> () noexcept

constexpr const T *	operator-> () const noexcept

constexpr T *	handle () noexcept

constexpr const T *	handle () const noexcept

constexpr void	swap (Wrapper &other) noexcept

constexpr void	swap (T &native) noexcept

Additional Inherited Members
Public Types inherited from opcua::Wrapper< T, Handler >
using	NativeType = T

using	HandlerType = Handler

Protected Member Functions inherited from opcua::Wrapper< T, Handler >
constexpr const T &	native () const noexcept

constexpr T &	native () noexcept

constexpr void	clear () noexcept

Related Symbols inherited from opcua::Wrapper< T, Handler >
template<typename T >
constexpr T *	asWrapper (typename T::NativeType *native) noexcept

template<typename T >
constexpr const T *	asWrapper (const typename T::NativeType *native) noexcept

template<typename T >
constexpr T &	asWrapper (typename T::NativeType &native) noexcept

template<typename T >
constexpr const T &	asWrapper (const typename T::NativeType &native) noexcept

template<typename T >
constexpr T::NativeType *	asNative (T *wrapper) noexcept

template<typename T >
constexpr const T::NativeType *	asNative (const T *wrapper) noexcept

template<typename T >
constexpr T::NativeType &	asNative (T &wrapper) noexcept

template<typename T >
constexpr const T::NativeType &	asNative (const T &wrapper) noexcept

Constructor & Destructor Documentation

◆ Variant() [1/6]

template<typename T , typename = std::enable_if_t<!std::is_const_v<T>>>

opcua::Variant::Variant ( T * ptr )

inlineexplicitnoexcept

Create Variant from a pointer to a scalar/array (no copy).

See also: assign(T*)

Definition at line 1061 of file types.hpp.

◆ Variant() [2/6]

template<typename T , typename = std::enable_if_t<!std::is_const_v<T>>>

opcua::Variant::Variant	(	T *	ptr,
		const UA_DataType &	type
	)

inlinenoexcept

Create Variant from a pointer to a scalar/array with a custom data type (no copy).

See also: assign(T*, const UA_DataType&)

Definition at line 1068 of file types.hpp.

◆ Variant() [3/6]

template<typename T , typename = std::enable_if_t<!isVariant<T>>>

opcua::Variant::Variant ( T && value )

inlineexplicit

Create Variant from a scalar/array (copy/move).

See also: assign(T&&)

Definition at line 1075 of file types.hpp.

◆ Variant() [4/6]

template<typename T >

opcua::Variant::Variant	(	T &&	value,
		const UA_DataType &	type
	)

inline

Create Variant from a scalar/array with a custom data type (copy/move).

See also: assign(T&&, const UA_DataType&)

Definition at line 1082 of file types.hpp.

◆ Variant() [5/6]

template<typename InputIt >

opcua::Variant::Variant	(	InputIt	first,
		InputIt	last
	)

inline

Create Variant from a range of elements (copy).

See also: assign(InputIt, InputIt)

Definition at line 1089 of file types.hpp.

◆ Variant() [6/6]

template<typename InputIt >

opcua::Variant::Variant	(	InputIt	first,
		InputIt	last,
		const UA_DataType &	type
	)

inline

Create Variant from a range of elements with a custom data type (copy).

See also: assign(InputIt, InputIt, const UA_DataType&)

Definition at line 1096 of file types.hpp.

Member Function Documentation

◆ array() [1/2]

template<typename T >

Span< T > opcua::Variant::array ( )

inline

Get array with given template type (only native or wrapper types).

Exceptions

BadVariantAccess If the variant is not an array or not of type `T`.

Examples: custom_datatypes/client_custom_datatypes.cpp.

Definition at line 1338 of file types.hpp.

◆ array() [2/2]

template<typename T >

Span< const T > opcua::Variant::array ( ) const

inline

Get array with given template type (only native or wrapper types).

Exceptions

BadVariantAccess If the variant is not an array or not of type `T`.

Definition at line 1345 of file types.hpp.

◆ arrayDimensions()

Span< const uint32_t > opcua::Variant::arrayDimensions ( ) const

inlinenoexcept

Get array dimensions.

Definition at line 1284 of file types.hpp.

◆ arrayLength()

size_t opcua::Variant::arrayLength ( ) const

inlinenoexcept

Get array length or 0 if variant is not an array.

Examples: typeconversion.cpp.

Definition at line 1279 of file types.hpp.

Referenced by array(), and array().

◆ assign() [1/8]

template<typename InputIt >

void opcua::Variant::assign	(	InputIt	first,
		InputIt	last
	)

inline

Assign range to variant (copy and convert if required).

Parameters

first	Iterator to the beginning of the range.
last	Iterator to the end of the range.

Template Parameters

InputIt Iterator of a container with native, wrapper or convertible elements.

Definition at line 1194 of file types.hpp.

◆ assign() [2/8]

template<typename InputIt >

void opcua::Variant::assign	(	InputIt	first,
		InputIt	last,
		const UA_DataType &	type
	)

inline

Assign range to variant with custom data type (copy).

Parameters

first	Iterator to the beginning of the range.
last	Iterator to the end of the range.
type	Custom data type.

Template Parameters

InputIt Iterator of a container with native or wrapper elements.

Definition at line 1212 of file types.hpp.

◆ assign() [3/8]

void opcua::Variant::assign ( std::nullptr_t ptr )

deletenoexcept

Examples: typeconversion.cpp.

Referenced by assign(), assign(), operator=(), operator=(), Variant(), Variant(), Variant(), Variant(), Variant(), and Variant().

◆ assign() [4/8]

void opcua::Variant::assign	(	std::nullptr_t	ptr,
		const UA_DataType &	type
	)

deletenoexcept

◆ assign() [5/8]

template<typename T >

void opcua::Variant::assign ( T && value )

inline

Assign scalar/array to variant (copy/move and convert if required).

Parameters

value

Value to copy to the variant. It can be:

A scalar native, wrapper or convertible value.
A container with native, wrapper or convertible elements. The container must implement begin() and end().

Definition at line 1155 of file types.hpp.

◆ assign() [6/8]

template<typename T >

void opcua::Variant::assign	(	T &&	value,
		const UA_DataType &	type
	)

inline

Assign scalar/array to variant with custom data type (copy/move).

Parameters

value	Value to copy to the variant. It can be: A scalar native or wrapper value. A container with native or wrapper elements. The container must implement `begin()` and `end()`.
type	Custom data type.

Definition at line 1178 of file types.hpp.

◆ assign() [7/8]

template<typename T , typename = std::enable_if_t<!std::is_const_v<T>>>

void opcua::Variant::assign ( T * ptr )

inlinenoexcept

Assign pointer to scalar/array to variant (no copy).

The object will not be deleted when the Variant is destructed.

Parameters

ptr

Non-const pointer to a value to assign to the variant. This can be:

A pointer to a scalar native or wrapper value.
A pointer to a contiguous container such as std::array or std::vector holding native or wrapper elements. The underlying array must be accessible with std::data and std::size.
A nullptr, in which case the variant will be cleared.

Definition at line 1120 of file types.hpp.

◆ assign() [8/8]

template<typename T , typename = std::enable_if_t<!std::is_const_v<T>>>

void opcua::Variant::assign	(	T *	ptr,
		const UA_DataType &	type
	)

inlinenoexcept

Assign pointer to scalar/array to variant with custom data type (no copy).

The object will not be deleted when the Variant is destructed.

Parameters

ptr	Non-const pointer to a value to assign to the variant. This can be: A pointer to a scalar native or wrapper value. A pointer to a contiguous container such as `std::array` or `std::vector` holding native or wrapper elements. The underlying array must be accessible with `std::data` and `std::size`. A `nullptr`, in which case the variant will be cleared.
type	Custom data type.

Definition at line 1137 of file types.hpp.

◆ data() [1/2]

const void * opcua::Variant::data ( ) const

inlinenoexcept

Get pointer to the underlying data.

Check the properties and data type before casting it to the actual type. Use the methods isScalar, isArray, isType / type.

Note: The UA_EMPTY_ARRAY_SENTINEL sentinel, used to indicate an empty array, is stripped from the returned pointer.

Definition at line 1304 of file types.hpp.

◆ data() [2/2]

void * opcua::Variant::data ( )

inlinenoexcept

Get pointer to the underlying data.

Check the properties and data type before casting it to the actual type. Use the methods isScalar, isArray, isType / type.

Note: The UA_EMPTY_ARRAY_SENTINEL sentinel, used to indicate an empty array, is stripped from the returned pointer.

Examples: custom_datatypes/client_custom_datatypes.cpp.

Definition at line 1299 of file types.hpp.

Referenced by array(), array(), data(), data(), scalar(), and scalar().

◆ empty()

bool opcua::Variant::empty ( ) const

inlinenoexcept

Check if the variant is empty.

Definition at line 1238 of file types.hpp.

Referenced by isArray().

◆ isArray()

bool opcua::Variant::isArray ( ) const

inlinenoexcept

Check if the variant is an array.

Examples: custom_datatypes/client_custom_datatypes.cpp.

Definition at line 1248 of file types.hpp.

◆ isScalar()

bool opcua::Variant::isScalar ( ) const

inlinenoexcept

Check if the variant is a scalar.

Examples: custom_datatypes/client_custom_datatypes.cpp.

Definition at line 1243 of file types.hpp.

Referenced by isArray().

◆ isType() [1/4]

template<typename T >

bool opcua::Variant::isType ( ) const

inlinenoexcept

Check if the variant type is equal to the provided template type.

Definition at line 1269 of file types.hpp.

Referenced by isType(), isType(), and isType().

◆ isType() [2/4]

bool opcua::Variant::isType ( const NodeId & id ) const

inlinenoexcept

Check if the variant type is equal to the provided data type id.

Definition at line 1263 of file types.hpp.

◆ isType() [3/4]

bool opcua::Variant::isType ( const UA_DataType & type ) const

inlinenoexcept

Check if the variant type is equal to the provided data type.

Definition at line 1258 of file types.hpp.

◆ isType() [4/4]

bool opcua::Variant::isType ( const UA_DataType * type ) const

inlinenoexcept

Check if the variant type is equal to the provided data type.

Examples: custom_datatypes/client_custom_datatypes.cpp.

Definition at line 1253 of file types.hpp.

◆ operator=() [1/2]

template<typename T , typename = std::enable_if_t<!isVariant<T>>>

Variant & opcua::Variant::operator= ( T && value )

inline

Assign scalar/array to variant (copy and convert if required).

See also: assign(T&&)

Definition at line 1227 of file types.hpp.

◆ operator=() [2/2]

template<typename T , typename = std::enable_if_t<!isVariant<T>>>

Variant & opcua::Variant::operator= ( T * value )

inlinenoexcept

Assign pointer to scalar/array to variant (no copy).

See also: assign(T*)

Definition at line 1219 of file types.hpp.

◆ scalar() [1/4]

template<typename T >

T & opcua::Variant::scalar ( ) &

inline

Get scalar value with given template type (only native or wrapper types).

Exceptions

BadVariantAccess If the variant is not a scalar or not of type `T`.

Examples: custom_datatypes/client_custom_datatypes.cpp, method/client_method_async.cpp, server_valuecallback.cpp, and typeconversion.cpp.

Definition at line 1311 of file types.hpp.

◆ scalar() [2/4]

template<typename T >

T opcua::Variant::scalar ( ) &&

inline

Get scalar value with given template type (only native or wrapper types).

Exceptions

BadVariantAccess If the variant is not a scalar or not of type `T`.

Definition at line 1325 of file types.hpp.

◆ scalar() [3/4]

template<typename T >

const T & opcua::Variant::scalar ( ) const &

inline

Get scalar value with given template type (only native or wrapper types).

Exceptions

BadVariantAccess If the variant is not a scalar or not of type `T`.

Definition at line 1318 of file types.hpp.

◆ scalar() [4/4]

template<typename T >

T opcua::Variant::scalar ( ) const &&

inline

Get scalar value with given template type (only native or wrapper types).

Exceptions

BadVariantAccess If the variant is not a scalar or not of type `T`.

Definition at line 1331 of file types.hpp.

◆ to() [1/2]

template<typename T >

T opcua::Variant::to ( ) &&

inline

Converts the variant to the specified type T with automatic conversion if required.

Determines the type category (scalar or array) based on the characteristics of T using type category detection. If T is a container, it must be constructible from an iterator pair.

// Scalar
opcua::Variant var{11};
const auto value = var.to<int>();

// Array
std::array<std::string, 3> array{"One", "Two", "Three"};
opcua::Variant var{array};
const auto vec = var.to<std::vector<std::string>>();
const auto lst = var.to<std::list<opcua::String>>();

Exceptions

BadVariantAccess If the variant is not convertible to `T`.

Definition at line 1380 of file types.hpp.

◆ to() [2/2]

template<typename T >

T opcua::Variant::to ( ) const &

inline

Converts the variant to the specified type T with automatic conversion if required.

Determines the type category (scalar or array) based on the characteristics of T using type category detection. If T is a container, it must be constructible from an iterator pair.

// Scalar
opcua::Variant var{11};
const auto value = var.to<int>();

// Array
std::array<std::string, 3> array{"One", "Two", "Three"};
opcua::Variant var{array};
const auto vec = var.to<std::vector<std::string>>();
const auto lst = var.to<std::list<opcua::String>>();

Exceptions

BadVariantAccess If the variant is not convertible to `T`.

Examples: server.cpp, server_datasource.cpp, and typeconversion.cpp.

Definition at line 1374 of file types.hpp.

◆ type()

const UA_DataType * opcua::Variant::type ( ) const

inlinenoexcept

Get data type.

Definition at line 1274 of file types.hpp.

Referenced by assign(), assign(), assign(), isType(), isType(), isType(), Variant(), Variant(), and Variant().

◆ Wrapper() [1/5]

constexpr opcua::Wrapper< T, Handler >::Wrapper ( )

constexprdefaultnoexcept

◆ Wrapper() [2/5]

constexpr opcua::Wrapper< T, Handler >::Wrapper ( const T & native )

inlineexplicitconstexpr

Copy constructor with native object.

Definition at line 151 of file wrapper.hpp.

◆ Wrapper() [3/5]

constexpr opcua::Wrapper< T, Handler >::Wrapper ( const Wrapper & other )

inlineconstexpr

Copy constructor.

Definition at line 147 of file wrapper.hpp.

◆ Wrapper() [4/5]

constexpr opcua::Wrapper< T, Handler >::Wrapper ( T && native )

inlineconstexprnoexcept

Move constructor with native object.

Definition at line 159 of file wrapper.hpp.

◆ Wrapper() [5/5]

constexpr opcua::Wrapper< T, Handler >::Wrapper ( Wrapper && other )

inlineconstexprnoexcept

Move constructor.

Definition at line 155 of file wrapper.hpp.

Detailed Description

Public Member Functions

Additional Inherited Members

Constructor & Destructor Documentation

◆ Variant() [1/6]

◆ Variant() [2/6]

◆ Variant() [3/6]

◆ Variant() [4/6]

◆ Variant() [5/6]

◆ Variant() [6/6]

Member Function Documentation

◆ array() [1/2]

◆ array() [2/2]

◆ arrayDimensions()

◆ arrayLength()

◆ assign() [1/8]

◆ assign() [2/8]

◆ assign() [3/8]

◆ assign() [4/8]

◆ assign() [5/8]

◆ assign() [6/8]

◆ assign() [7/8]

◆ assign() [8/8]

◆ data() [1/2]

◆ data() [2/2]

◆ empty()

◆ isArray()

◆ isScalar()

◆ isType() [1/4]

◆ isType() [2/4]

◆ isType() [3/4]

◆ isType() [4/4]

◆ operator=() [1/2]

◆ operator=() [2/2]

◆ scalar() [1/4]

◆ scalar() [2/4]

◆ scalar() [3/4]

◆ scalar() [4/4]

◆ to() [1/2]

◆ to() [2/2]

◆ type()

◆ Wrapper() [1/5]

◆ Wrapper() [2/5]

◆ Wrapper() [3/5]

◆ Wrapper() [4/5]

◆ Wrapper() [5/5]