Acts::Result< void, E > Class Template Reference

Template specialization for the void case. More...

#include <Acts/Utilities/Result.hpp>

Inheritance diagram for Acts::Result< void, E >:

Collaboration diagram for Acts::Result< void, E >:

Public Types
using	ErrorType = E
	Type alias for the error type contained in failed result.
using	ValueType = void
	Type alias for the value type (void) in successful result.

Public Member Functions
	Result ()=default
	Default constructor which initializes the result in the ok state.
	Result (const Result< void, E > &other)=default
	The copy constructor is deleted.
template<typename E2>
	Result (E2 error) noexcept
	Constructor from error.
	Result (Result< void, E > &&other) noexcept
	Move constructor.
auto	and_then (C &&callable) const &
	Bind a function to this result monadically.
E	error () &&noexcept
	Returns the error by-value.
E &	error () &noexcept
	Returns a reference to the error stored in the result.
const E &	error () const &noexcept
	Returns a reference to the error stored in the result.
bool	ok () const noexcept
	Checks whether this result is in the ok state, and no error.
void &	operator* () noexcept
	Returns a reference into the variant to the valid value.
void *	operator-> () noexcept
	Allows to access members of the stored object with res->foo similar to std::optional.
Result< void, E > &	operator= (const Result< void, E > &other)=default
	The (self) assignment operator is deleted.
template<typename E2>
Result< void, E > &	operator= (E2 error)
	Assignment operator from an error.
Result< void, E > &	operator= (Result< void, E > &&other) noexcept
	Move assignment operator.
auto	transform (C &&callable) const &
	Transforms the value contained in this result.
void	value () const
	Validates this void result and throws if an error is present.
std::conditional_t< std::is_reference_v< U >, const void &, void >	value_or (U &&v) const &
	Retrieves the valid value from the result object, or returns a default value if no valid value exists.

Static Public Member Functions
static Result< void, E >	failure (E error)
	Static factory function to initialize the result in the error state.
static Result< void, E >	success ()
	Static factory function to initialize the result in the ok state.

Detailed Description

template<typename E>
class Acts::Result< void, E >

Template specialization for the void case.

This specialization handles the case where there is no actual return value, but an error might be returned. Returning the error directly would make handling different from other functions using the Result<T, E> mechanism. Result<void, E> does not have the dereference operator, and value methods. The static success factory does not accept a value.

Note

To ease usage, this Result<void, E> is default constructible in the ok state, whereas Result<T, E> is not.

Template Parameters

E	The type of the error

Constructor & Destructor Documentation

Result() [1/3]

template<typename E>

Acts::Result< void, E >::Result ( const Result< void, E > & other )

default

The copy constructor is deleted.

Parameters

other

The other result instance to copy from

Result() [2/3]

template<typename E>

Acts::Result< void, E >::Result ( Result< void, E > && other )

noexcept

Move constructor.

Parameters

other

The other result object, rvalue ref

Result() [3/3]

template<typename E>

template<typename E2>

Acts::Result< void, E >::Result ( E2 error )

noexcept

Constructor from error.

This implicitly requires E2 to be convertible to E.

Template Parameters

E2	The type of the actual error

Parameters

error

The instance of the actual error

Member Function Documentation

and_then()

auto Acts::Result< void, E >::and_then

(

C &&

callable

)

const &

Bind a function to this result monadically.

This function takes a function f and, if this result contains a valid value x, returns f(x). If the type of x is T, then f is expected to accept type T and return Result<U>. In this case, transform would return the unhelpful type Result<Result<U>>, so and_then strips away the outer layer to return Result<U>. If the value is invalid, this returns an invalid value in Result<U>.

Parameters

[in]

callable

The transformation function to apply.

Note

This is the lvalue version.

This functions is >>= on the functor in A of Result<A, E>.

Returns

The modified valid value if exists, or an error otherwise.

error() [1/3]

template<typename E>

E Acts::Result< void, E >::error ( ) &&

noexcept

Returns the error by-value.

Note

If res.ok() this method will abort (noexcept)

Returns

The error by value

error() [2/3]

template<typename E>

E & Acts::Result< void, E >::error ( ) &

noexcept

Returns a reference to the error stored in the result.

Note

If res.ok() this method will abort (noexcept)

Returns

Reference to the error

error() [3/3]

template<typename E>

const E & Acts::Result< void, E >::error ( ) const &

noexcept

Returns a reference to the error stored in the result.

Note

If res.ok() this method will abort (noexcept)

Returns

Reference to the error

failure()

template<typename E>

Result< void, E > Acts::Result< void, E >::failure ( E error )

static

Static factory function to initialize the result in the error state.

Parameters

error

The error to initialize with.

Returns

Result object, in error state.

ok()

template<typename E>

bool Acts::Result< void, E >::ok ( ) const

noexcept

Checks whether this result is in the ok state, and no error.

Returns

bool Whether result contains an error or not.

operator*()

void & Acts::Result< void, E >::operator* ( )

noexcept

Returns a reference into the variant to the valid value.

Note

If !res.ok(), this method will abort (noexcept)

Returns

Reference to value stored in the variant.

operator->()

void * Acts::Result< void, E >::operator-> ( )

noexcept

Allows to access members of the stored object with res->foo similar to std::optional.

Note

If !res.ok(), this method will abort (noexcept)

Returns

Pointer to value stored in the variant.

operator=() [1/3]

template<typename E>

Result< void, E > & Acts::Result< void, E >::operator= ( const Result< void, E > & other )

default

The (self) assignment operator is deleted.

Parameters

other

The other result instance to assign from

Returns

Reference to this result instance

operator=() [2/3]

template<typename E>

template<typename E2>

Result< void, E > & Acts::Result< void, E >::operator=

(

E2

error

)

Assignment operator from an error.

Template Parameters

E2	The type of the actual error

Parameters

error

The instance of the actual error

Returns

The assigned instance

operator=() [3/3]

template<typename E>

Result< void, E > & Acts::Result< void, E >::operator= ( Result< void, E > && other )

noexcept

Move assignment operator.

Parameters

other

The other result object, rvalue ref

Returns

Reference to this result for assignment chaining

success()

template<typename E>

Result< void, E > Acts::Result< void, E >::success ( )

static

Static factory function to initialize the result in the ok state.

Returns

Result object, in ok state

transform()

auto Acts::Result< void, E >::transform

(

C &&

callable

)

const &

Transforms the value contained in this result.

Applying a function f to a valid value x returns f(x), while applying f to an invalid value returns another invalid value.

Parameters

[in]

callable

The transformation function to apply.

Note

This is the lvalue version.

This functions is fmap on the functor in A of Result<A, E>.

Returns

The modified valid value if exists, or an error otherwise.

value()

template<typename E>

void Acts::Result< void, E >::value

(

)

const

Validates this void result and throws if an error is present.

This method checks if the result contains an error and throws an exception if one is found. For void results, there is no value to return - this method only performs validation.

Exceptions

std::runtime_error

if the result contains an error

value_or()

std::conditional_t< std::is_reference_v< U >, const void &, void > Acts::Result< void, E >::value_or

(

U &&

v

)

const &

Retrieves the valid value from the result object, or returns a default value if no valid value exists.

Parameters

[in]

v

The default value to use if no valid value exists.

Note

This is the lvalue version.

This function always returns by value.

Returns

Either the valid value, or the given substitute.