Generic Enumeration

Result

A value that represents either a success or a failure, including an associated value in each case.

Declaration

@frozen enum Result<Success, Failure> where Failure : Error

Topics

Representing a Result

case success(Success)

A success, storing a Success value.

case failure(Failure)

A failure, storing a Failure value.

Writing Failable Asynchronous APIs

Vend results as part of an API when you can’t return errors synchronously.

Converting a Throwing Expression to a Result

Preserving the Results of a Throwing Expression

Call the initializer that wraps a throwing expression when you need to serialize or memoize the result.

init(catching: () -> Success)

Creates a new result by evaluating a throwing closure, capturing the returned value as a success, or any thrown error as a failure.

Converting a Result to a Throwing Expression

func get() -> Success

Returns the success value as a throwing expression.

Transforming a Result

func map<NewSuccess>((Success) -> NewSuccess) -> Result<NewSuccess, Failure>

Returns a new result, mapping any success value using the given transformation.

func mapError<NewFailure>((Failure) -> NewFailure) -> Result<Success, NewFailure>

Returns a new result, mapping any failure value using the given transformation.

func flatMap<NewSuccess>((Success) -> Result<NewSuccess, Failure>) -> Result<NewSuccess, Failure>

Returns a new result, mapping any success value using the given transformation and unwrapping the produced result.

func flatMapError<NewFailure>((Failure) -> Result<Success, NewFailure>) -> Result<Success, NewFailure>

Returns a new result, mapping any failure value using the given transformation and unwrapping the produced result.

Comparing Results

static func != (Result<Success, Failure>, Result<Success, Failure>) -> Bool

Publishing a Result

struct Result.Publisher

A Combine publisher that publishes a result and then finishes normally, or fails without publishing any elements.

Instance Properties

var hashValue: Int

The hash value.

Available when Success conforms to Hashable and Failure conforms to Hashable.

var publisher: Result<Success, Failure>.Publisher

Instance Methods

func hash(into: inout Hasher)

Hashes the essential components of this value by feeding them into the given hasher.

Available when Success conforms to Hashable and Failure conforms to Hashable.

Operator Functions

static func == (Result<Success, Failure>, Result<Success, Failure>) -> Bool

Returns a Boolean value indicating whether two values are equal.

Available when Success conforms to Equatable and Failure conforms to Equatable.

Relationships

Conforms To

Equatable
Conforms when Success conforms to Equatable and Failure conforms to Equatable.
Hashable
Conforms when Success conforms to Hashable and Failure conforms to Hashable.