opcua::Result< T > Class Template Reference

#include <result.hpp>

Detailed Description

template<typename T>
class opcua::Result< T >

The template class Result encapsulates a StatusCode and optionally a value.

A result may have one of the following contents:

• a value and a StatusCode (usually good or uncertain)
• no value and a bad StatusCode

Result<void> is a template specialization containing only a StatusCode.

The design is inspired by:

• C++ 23's std::expected type
• Rust's Result type
• Swift's Result enumeration

Examples

client_async.cpp.

Definition at line 53 of file result.hpp.

Public Types
using	ValueType = T

Public Member Functions
constexpr	Result () noexcept(std::is_nothrow_default_constructible_v< T >)
constexpr	Result (const T &value, StatusCode code=UA_STATUSCODE_GOOD) noexcept(std::is_nothrow_copy_constructible_v< T >)
constexpr	Result (T &&value, StatusCode code=UA_STATUSCODE_GOOD) noexcept(std::is_nothrow_move_constructible_v< T >)
constexpr	Result (BadResult error) noexcept
constexpr T *	operator-> () noexcept
constexpr const T *	operator-> () const noexcept
constexpr T &	operator* () &noexcept
constexpr const T &	operator* () const &noexcept
constexpr T &&	operator* () &&noexcept
constexpr const T &&	operator* () const &&noexcept
constexpr StatusCode	code () const noexcept
constexpr	operator bool () const noexcept
constexpr bool	hasValue () const noexcept
constexpr T &	value () &
constexpr const T &	value () const &
constexpr T &&	value () &&
constexpr const T &&	value () const &&
template<typename U >
constexpr T	valueOr (U &&defaultValue) const &
template<typename U >
constexpr T	valueOr (U &&defaultValue) &&
template<typename F >
constexpr auto	transform (F &&func) &
template<typename F >
constexpr auto	transform (F &&func) const &
template<typename F >
constexpr auto	transform (F &&func) &&
template<typename F >
constexpr auto	transform (F &&func) const &&
template<typename F >
constexpr auto	andThen (F &&func) &
template<typename F >
constexpr auto	andThen (F &&func) const &
template<typename F >
constexpr auto	andThen (F &&func) &&
template<typename F >
constexpr auto	andThen (F &&func) const &&
template<typename F >
constexpr auto	orElse (F &&func) &
template<typename F >
constexpr auto	orElse (F &&func) const &
template<typename F >
constexpr auto	orElse (F &&func) &&
template<typename F >
constexpr auto	orElse (F &&func) const &&

Member Typedef Documentation

ValueType

template<typename T >

using opcua::Result< T >::ValueType = T

Definition at line 55 of file result.hpp.

Constructor & Destructor Documentation

Result() [1/4]

template<typename T >

opcua::Result< T >::Result ( )

inlineconstexprnoexcept

Default constructor (default-initialized value and good StatusCode).

Definition at line 60 of file result.hpp.

Result() [2/4]

template<typename T >

opcua::Result< T >::Result ( const T & value, StatusCode code = UA_STATUSCODE_GOOD )

inlineconstexprnoexcept

Construct a Result from a value (lvalue) and a StatusCode.

Definition at line 69 of file result.hpp.

Result() [3/4]

template<typename T >

opcua::Result< T >::Result ( T && value, StatusCode code = UA_STATUSCODE_GOOD )

inlineconstexprnoexcept

Construct a Result from a value (rvalue) and a StatusCode.

Definition at line 78 of file result.hpp.

Result() [4/4]

template<typename T >

opcua::Result< T >::Result ( BadResult< T > error )

inlineconstexprnoexcept

Construct a Result from a BadResult.

Definition at line 87 of file result.hpp.

Member Function Documentation

operator->() [1/2]

template<typename T >

T * opcua::Result< T >::operator-> ( )

inlineconstexprnoexcept

Get the value of the Result.

Accessing a Result without a value leads to undefined behavior.

Definition at line 99 of file result.hpp.

operator->() [2/2]

template<typename T >

const T * opcua::Result< T >::operator-> ( ) const

inlineconstexprnoexcept

Get the value of the Result.

Accessing a Result without a value leads to undefined behavior.

Definition at line 104 of file result.hpp.

operator*() [1/4]

template<typename T >

T & opcua::Result< T >::operator* ( ) &

inlineconstexprnoexcept

Get the value of the Result.

Accessing a Result without a value leads to undefined behavior.

Definition at line 112 of file result.hpp.

operator*() [2/4]

template<typename T >

const T & opcua::Result< T >::operator* ( ) const &

inlineconstexprnoexcept

Get the value of the Result.

Accessing a Result without a value leads to undefined behavior.

Definition at line 117 of file result.hpp.

operator*() [3/4]

template<typename T >

T && opcua::Result< T >::operator* ( ) &&

inlineconstexprnoexcept

Get the value of the Result.

Accessing a Result without a value leads to undefined behavior.

Definition at line 122 of file result.hpp.

operator*() [4/4]

template<typename T >

const T && opcua::Result< T >::operator* ( ) const &&

inlineconstexprnoexcept

Get the value of the Result.

Accessing a Result without a value leads to undefined behavior.

Definition at line 127 of file result.hpp.

code()

template<typename T >

StatusCode opcua::Result< T >::code ( ) const

inlineconstexprnoexcept

Get the StatusCode of the Result.

Examples

client_async.cpp.

Definition at line 136 of file result.hpp.

operator bool()

template<typename T >

opcua::Result< T >::operator bool ( ) const

inlineexplicitconstexprnoexcept

Check if the Result has a value.

Definition at line 143 of file result.hpp.

hasValue()

template<typename T >

bool opcua::Result< T >::hasValue ( ) const

inlineconstexprnoexcept

Check if the Result has a value.

Definition at line 150 of file result.hpp.

value() [1/4]

template<typename T >

T & opcua::Result< T >::value ( ) &

inlineconstexpr

Get the value of the Result.

Exceptions

BadStatus

If the Result does not have a value (bad StatusCode).

Examples

client_async.cpp.

Definition at line 158 of file result.hpp.

value() [2/4]

template<typename T >

const T & opcua::Result< T >::value ( ) const &

inlineconstexpr

Get the value of the Result.

Exceptions

BadStatus

If the Result does not have a value (bad StatusCode).

Definition at line 164 of file result.hpp.

value() [3/4]

template<typename T >

T && opcua::Result< T >::value ( ) &&

inlineconstexpr

Get the value of the Result.

Exceptions

BadStatus

If the Result does not have a value (bad StatusCode).

Definition at line 170 of file result.hpp.

value() [4/4]

template<typename T >

const T && opcua::Result< T >::value ( ) const &&

inlineconstexpr

Get the value of the Result.

Exceptions

BadStatus

If the Result does not have a value (bad StatusCode).

Definition at line 176 of file result.hpp.

valueOr() [1/2]

template<typename T >

template<typename U >

T opcua::Result< T >::valueOr ( U && defaultValue ) const &

inlineconstexpr

Get the value of the Result or a default value.

The default value is returned in case of an bad StatusCode.

Definition at line 186 of file result.hpp.

valueOr() [2/2]

template<typename T >

template<typename U >

T opcua::Result< T >::valueOr ( U && defaultValue ) &&

inlineconstexpr

Get the value of the Result or a default value.

The default value is returned in case of an bad StatusCode.

Definition at line 192 of file result.hpp.

transform() [1/4]

template<typename T >

template<typename F >

auto opcua::Result< T >::transform ( F && func ) &

inlineconstexpr

Transforms Result<T> to Result<U> using the given value transformation function.

The function is only applied if the Result has a value. Otherwise Result<U> with the same bad StatusCode is returned.

Parameters

func	Callable with the signature U(T&&)

Definition at line 203 of file result.hpp.

transform() [2/4]

template<typename T >

template<typename F >

auto opcua::Result< T >::transform ( F && func ) const &

inlineconstexpr

Transforms Result<T> to Result<U> using the given value transformation function.

The function is only applied if the Result has a value. Otherwise Result<U> with the same bad StatusCode is returned.

Parameters

func	Callable with the signature U(T&&)

Definition at line 209 of file result.hpp.

transform() [3/4]

template<typename T >

template<typename F >

auto opcua::Result< T >::transform ( F && func ) &&

inlineconstexpr

Transforms Result<T> to Result<U> using the given value transformation function.

The function is only applied if the Result has a value. Otherwise Result<U> with the same bad StatusCode is returned.

Parameters

func	Callable with the signature U(T&&)

Definition at line 215 of file result.hpp.

transform() [4/4]

template<typename T >

template<typename F >

auto opcua::Result< T >::transform ( F && func ) const &&

inlineconstexpr

Transforms Result<T> to Result<U> using the given value transformation function.

The function is only applied if the Result has a value. Otherwise Result<U> with the same bad StatusCode is returned.

Parameters

func	Callable with the signature U(T&&)

Definition at line 221 of file result.hpp.

andThen() [1/4]

template<typename T >

template<typename F >

auto opcua::Result< T >::andThen ( F && func ) &

inlineconstexpr

Transforms Result<T> to Result<U> using the given function.

The function is only applied if the Result has a value. Otherwise Result<U> with the same bad StatusCode is returned.

Parameters

func	Callable with the signature Result<U>(T&&) or Result<U>(T&&, StatusCode)

Definition at line 232 of file result.hpp.

andThen() [2/4]

template<typename T >

template<typename F >

auto opcua::Result< T >::andThen ( F && func ) const &

inlineconstexpr

Transforms Result<T> to Result<U> using the given function.

The function is only applied if the Result has a value. Otherwise Result<U> with the same bad StatusCode is returned.

Parameters

func	Callable with the signature Result<U>(T&&) or Result<U>(T&&, StatusCode)

Definition at line 238 of file result.hpp.

andThen() [3/4]

template<typename T >

template<typename F >

auto opcua::Result< T >::andThen ( F && func ) &&

inlineconstexpr

Transforms Result<T> to Result<U> using the given function.

The function is only applied if the Result has a value. Otherwise Result<U> with the same bad StatusCode is returned.

Parameters

func	Callable with the signature Result<U>(T&&) or Result<U>(T&&, StatusCode)

Definition at line 244 of file result.hpp.

andThen() [4/4]

template<typename T >

template<typename F >

auto opcua::Result< T >::andThen ( F && func ) const &&

inlineconstexpr

Transforms Result<T> to Result<U> using the given function.

The function is only applied if the Result has a value. Otherwise Result<U> with the same bad StatusCode is returned.

Parameters

func	Callable with the signature Result<U>(T&&) or Result<U>(T&&, StatusCode)

Definition at line 250 of file result.hpp.

orElse() [1/4]

template<typename T >

template<typename F >

auto opcua::Result< T >::orElse ( F && func ) &

inlineconstexpr

Transforms Result<T> with a bad StatusCode to Result<T> using the given function.

The function is only applied if the Result has no value. Otherwise the same Result<T> is returned.

Parameters

func	Callable with the signature Result<T>(StatusCode)

Definition at line 261 of file result.hpp.

orElse() [2/4]

template<typename T >

template<typename F >

auto opcua::Result< T >::orElse ( F && func ) const &

inlineconstexpr

Transforms Result<T> with a bad StatusCode to Result<T> using the given function.

The function is only applied if the Result has no value. Otherwise the same Result<T> is returned.

Parameters

func	Callable with the signature Result<T>(StatusCode)

Definition at line 267 of file result.hpp.

orElse() [3/4]

template<typename T >

template<typename F >

auto opcua::Result< T >::orElse ( F && func ) &&

inlineconstexpr

Transforms Result<T> with a bad StatusCode to Result<T> using the given function.

The function is only applied if the Result has no value. Otherwise the same Result<T> is returned.

Parameters

func	Callable with the signature Result<T>(StatusCode)

Definition at line 273 of file result.hpp.

orElse() [4/4]

template<typename T >

template<typename F >

auto opcua::Result< T >::orElse ( F && func ) const &&

inlineconstexpr

Transforms Result<T> with a bad StatusCode to Result<T> using the given function.

The function is only applied if the Result has no value. Otherwise the same Result<T> is returned.

Parameters

func	Callable with the signature Result<T>(StatusCode)

Definition at line 279 of file result.hpp.