Promise

public final class Promise<Value>

A promise represents the eventual result of an asynchronous operation. The primary way of interacting with a promise is through its then method, which registers callbacks to receive either a promise’s eventual value or the reason why the promise cannot be fulfilled.

  • Wrap creating a promise in a promise.

    Declaration

    Swift

    public class func `try`(_ makePromise: () throws -> Promise) -> Promise

    Parameters

    makePromise

    block which creates a promise. Errors thrown will be reflected in the returned promise.

    Return Value

    the promise returned by makePromise, or rejected by an error thrown by makePromise.

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  • Initialize a new promise. Callbacks will be performed by calling dispatch.

    Declaration

    Swift

    public required init(dispatch: @escaping (@escaping () -> Void) -> Void = { $0() })

    Parameters

    dispatch

    block used to execute callbacks.
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  • Fulfills this promise with a value. Any previous or future calls to then() will be completed with value. If this promise has already been fulfilled or rejected, this function does nothing.

    Declaration

    Swift

    public func fulfill(with value: Value)

    Parameters

    value

    the value fulfilling this promise.
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  • Returns a function which fulfills a promise with a value. Any previous or future calls to promise.then() will be fulfilled with value. If the promise has already been fulfilled or rejected, the returned function does nothing.

    Declaration

    Swift

    public static func fulfill(with value: @autoclosure @escaping () -> Value) -> (Promise) -> Void

    Parameters

    value

    the value to fulfill Promises with.
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  • Rejects this promise with an error. Any previous or future calls to catch() will be completed with error. If this promise has already been fulfilled or rejected, this function does nothing.

    Declaration

    Swift

    public func reject(with error: Error)

    Parameters

    error

    the error rejecting this promise.
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  • Returns a function which rejects a promise with an error. Any previous or future calls to promise.catch() will be completed with error. If the promise has already been fulfilled or rejected, the returned function does nothing.

    Declaration

    Swift

    public static func reject(with error: @autoclosure @escaping () -> Error) -> (Promise) -> Void

    Parameters

    error

    the error rejecting this promise.
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  • Register a completion to be called when this promise is fulfilled. If this promise has already been fulfilled, completion will still be called. If this promise is rejected, completion will not be called.

    Declaration

    Swift

    public func then(_ fulfillment: @autoclosure @escaping () -> (Value) -> Void) -> Promise

    Parameters

    completion

    the completion to be called upon fulfillment.

    Return Value

    self

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  • Register a completion to be called when this promise is fulfilled. If this promise has already been fulfilled, completion will still be called. If this promise is rejected, completion will not be called.

    The value this promise was fulfilled with will fulfill the returned promise, unless an error is thrown by completion, which will reject the promise instead.

    Declaration

    Swift

    public func then(_ fulfillment: @autoclosure @escaping () -> (Value) throws -> Void) -> Promise

    Parameters

    completion

    the completion to be called upon fulfillment.

    Return Value

    a new promise to be fulfilled or rejected by completion.

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  • Register a completion to be called when this promise is fulfilled. If this promise has already been fulfilled, completion will still be called. If this promise is rejected, completion will not be called.

    The value returned by completion will fulfill the returned promise, unless an error is thrown, which will reject the promise instead.

    Declaration

    Swift

    public func then<NewValue>(_ fulfillment: @autoclosure @escaping () -> (Value) throws -> NewValue) -> Promise<NewValue>

    Parameters

    completion

    the completion to be called upon fulfillment.

    Return Value

    a new promise to be fulfilled or rejected by completion.

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  • Register a completion to be called when this promise is fulfilled. If this promise has already been fulfilled, completion will still be called. If this promise is rejected, completion will not be called.

    The promise returned by completion will be used to fulfill or reject the returned promise.

    Declaration

    Swift

    public func then<NewValue>(_ fulfillment: @autoclosure @escaping () -> (Value) -> NewValue) -> Promise<NewValue>

    Parameters

    completion

    the completion to be called upon fulfillment.

    Return Value

    a new promise to be fulfilled or rejected by completion.

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  • Register a completion to be called when this promise is rejected. If this promise has already been rejected, completion will still be called. If this promise is fulfilled, completion will not be called.

    Declaration

    Swift

    public func `catch`(_ rejection: @autoclosure @escaping () -> (Error) -> Void) -> Promise

    Parameters

    completion

    the completion to be called upon rejection.

    Return Value

    self

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  • Register a completion to be called when this promise is fulfilled or rejected. If this promise has already been fulfilled or rejected, completion will still be called.

    Declaration

    Swift

    public func finally(_ completion: @autoclosure @escaping () -> () -> Void) -> Promise

    Parameters

    completion

    the completion to be called upon fulfillment or rejection.

    Return Value

    self

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  • Create a new promise fulfilled or rejected by this promise which runs any completions on queue.

    Declaration

    Swift

    public static func async(with queue: DispatchQueue) -> (Promise) -> Promise

    Parameters

    queue

    a dispatch queue on which to run completions.

    Return Value

    a block returning new promise to be fulfilled or rejected by the provided promise.

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  • Create a new promise fulfilled or rejected by this promise which runs any completions on queue.

    Declaration

    Swift

    public func async(with queue: DispatchQueue) -> Promise

    Parameters

    queue

    a dispatch queue on which to run completions.

    Return Value

    a new promise to be fulfilled or rejected by self.

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  • Create a new promise fulfilled or rejected by promise which runs any completions on the main thread.

    Declaration

    Swift

    public static func main(_ promise: Promise) -> Promise

    Return Value

    a new promise to be fulfilled or rejected by promise.

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  • Create a new promise fulfilled or rejected by this promise which runs any completions on the main thread.

    Declaration

    Swift

    public func main() -> Promise

    Return Value

    a new promise to be fulfilled or rejected by self.

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  • Fulfill or reject this promise with a Result.

    Declaration

    Swift

    public func complete<E>(with result: Result<Value, E>)

    Parameters

    result

    the result containing a value which will fulfill or reject self.
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  • Create a Promise fulfilled or rejected by the given Result.

    Declaration

    Swift

    public convenience init<E>(result: Result<Value, E>)

    Parameters

    result

    the result containing a value which will fulfill or reject self.
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  • Register a completion to be called when this promise is fulfilled. If this promise has already been fulfilled, completion will still be called. If this promise is rejected, completion will not be called.

    Declaration

    Swift

    public static func ?>(promise: Promise, f: @autoclosure @escaping () -> (Value) -> Void) -> Promise

    Parameters

    promise

    the promise on which to add the fulfillment.
    completion

    the completion to be called upon fulfillment.

    Return Value

    promise

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  • Register a completion to be called when this promise is fulfilled. If this promise has already been fulfilled, completion will still be called. If this promise is rejected, completion will not be called.

    The value this promise was fulfilled with will fulfill the returned promise, unless an error is thrown by completion, which will reject the promise instead.

    Declaration

    Swift

    public static func ?>(promise: Promise, f: @autoclosure @escaping () -> (Value) throws -> Void) -> Promise

    Parameters

    promise

    the promise on which to add the fulfillment.
    completion

    the completion to be called upon fulfillment.

    Return Value

    a new promise to be fulfilled or rejected by completion.

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  • Register a completion to be called when this promise is fulfilled. If this promise has already been fulfilled, completion will still be called. If this promise is rejected, completion will not be called.

    The promise returned by completion will be used to fulfill or reject the returned promise.

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    Declaration

    Swift

    public static func ?><NewValue>(promise: Promise, f: @autoclosure @escaping () -> (Value) -> NewValue) -> Promise<NewValue>

    Parameters

    promise

    the promise on which to add the fulfillment.
    completion

    the completion to be called upon fulfillment.

    Return Value

    a new promise to be fulfilled or rejected by completion.

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  • Register a completion to be called when this promise is fulfilled. If this promise has already been fulfilled, completion will still be called. If this promise is rejected, completion will not be called.

    The value returned by completion will fulfill the returned promise, unless an error is thrown, which will reject the promise instead.

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    Declaration

    Swift

    public static func ?><NewValue>(promise: Promise, f: @autoclosure @escaping () -> (Value) throws -> NewValue) -> Promise<NewValue>

    Parameters

    promise

    the promise on which to add the fulfillment.
    completion

    the completion to be called upon fulfillment.

    Return Value

    a new promise to be fulfilled or rejected by completion.

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  • Register a completion to be called when this promise is rejected. If this promise has already been rejected, completion will still be called. If this promise is fulfilled, completion will not be called.

    Declaration

    Swift

    public static func !>(promise: Promise, f: @autoclosure @escaping () -> (Error) -> Void) -> Promise

    Parameters

    promise

    the promise on which to add the completion.
    completion

    the completion to be called upon rejection.

    Return Value

    promise.

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  • Register a completion to be called when this promise is fulfilled or rejected. If this promise has already been fulfilled or rejected, completion will still be called.

    Declaration

    Swift

    public static func *>(promise: Promise, f: @autoclosure @escaping () -> () -> Void) -> Promise

    Parameters

    promise

    the promise on which to add the completion.
    completion

    the completion to be called upon fulfillment or rejection.

    Return Value

    promise.

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