Class Acts::Result

template<typename T, typename E = std::error_code> class Result

Class which encapsulates either a valid result, or an error.

Template Parameters

T – The valid result value
E – The error, defaults to std::error_code

Public Functions

Result() = delete: Default construction is disallowed.

Result(const Result<T, E> &other) = delete: Copy construction is disallowed.

inline Result(Result<T, E> &&other): Move construction is allowed.

template<typename T2, typename _E = E, typename _T = T, typename = std::enable_if_t<(!std::is_same_v<_T, _E> && !std::is_constructible_v<_T, _E> && !std::is_convertible_v<_T, _E> && !std::is_constructible_v<_E, _T> && !std::is_convertible_v<_E, _T> && !(std::is_convertible_v<T2, _T> && std::is_convertible_v<T2, _E>))>> inline Result(T2 value) noexcept

Constructor from arbitrary value This constructor allows construction from any value.

This constructor is only enabled if T and E are unambiguous, meaning the cannot be implicitly converted and there is T cannot be constructed from E and vice-versa. This means that when this is invoked, the value can be propagated to the underlying variant, and the assignment will be correct, and error will be an error, and a value will be a value.

Note

If T and E are ambiguous, use the success and failure static factory methods.

Template Parameters: T2 – Type of the potential assignment
Parameters: value – The potential value, could be an actual valid value or an error.

inline E error() && noexcept

Returns the error by-value.

Note

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

Returns: The error

inline 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

inline bool ok() const noexcept

Checks whether this result contains a valid value, and no error.

Returns: bool Whether result contains an error or not.

inline T &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.

inline T *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.

Result<T, E> &operator=(const Result<T, E> &other) = delete: Assignment is disallowed.

inline Result<T, E> &operator=(Result<T, E> &&other)

Move assignment is allowed.

Parameters: other – The other result instance, rvalue reference
Returns: The assigned instance

template<typename T2, typename _E = E, typename _T = T, typename = std::enable_if_t<(!std::is_same_v<_T, _E> && !std::is_constructible_v<_T, _E> && !std::is_convertible_v<_T, _E> && !std::is_constructible_v<_E, _T> && !std::is_convertible_v<_E, _T> && !(std::is_convertible_v<T2, _T> && std::is_convertible_v<T2, _E>))>> inline Result<T, E> &operator=(T2 value) noexcept

Assignment operator from arbitrary value This operator allows construction from any value.

The same rules as for the Result(T2 value) constructor apply.

Template Parameters: T2 – Type of the potential assignment
Parameters: value – The potential value, could be an actual valid value or an error.
Returns: The assigned instance

inline T &value() &

Retrieves the valid value from the result object.

Note

This is the lvalue version, returns a reference to the value

Returns: The valid value as a reference

inline T value() &&

Retrieves the valid value from the result object.

Note

This is the rvalue version, returns the value by-value and moves out of the variant.

Returns: The valid value by value, moved out of the variant.

Public Static Functions

static inline Result<T, E> failure(E error)

Static helper factory which forces assignment as an error.

Parameters: error – The error to assign. Will not be converted to T.
Returns: Initialized result object

static inline Result<T, E> success(T value)

Static helper factory which forces assignment as valid value.

Parameters: value – The valid value to assign. Will not be converted to E.
Returns: Initialized result object