Skip to content

Latest commit

 

History

History
287 lines (205 loc) · 8.26 KB

README.md

File metadata and controls

287 lines (205 loc) · 8.26 KB

SwiftTask

Promise + progress + pause + cancel, using SwiftState (state machine).

SwiftTask

Example

Basic

// define task
let task = Task<Float, String, NSError> { (progress, fulfill, reject, configure) in

    player.doSomethingWithProgress({ (progressValue: Float) in
        progress(progressValue) // optional
    }, completion: { (value: NSData?, error: NSError?) in
        if error == nil {
            fulfill("OK")
        }
        else {
            reject(error)
        }
    })

    // pause/resume/cancel configuration (optional)
    configure.pause = { [weak player] in
        if let p = player { p.pause() }
    }
    configure.resume = { [weak player] in
        if let p = player { p.resume() }
    }
    configure.cancel = { [weak player] in
        if let p = player { p.cancel() }
    }

}

// set then & catch
task.then { (value: String) -> Void in
    // do something with fulfilled value
}.catch { (error: NSError?, isCancelled: Bool) -> Void in
    // do something with rejected error
}

// you can call configured operations outside of Task-definition
task.pause()
task.resume()
task.cancel()

Notice that player has following methods, which will work nicely with SwiftTask:

  • doSomethingWithProgress(_:completion:) (progress callback as optional)
  • pause() (optional)
  • resume() (optional)
  • cancel() (optional)

One of the best example would be Alamofire (networking library) as seen below.

Using Alamofire

typealias Progress = (bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64)

// define task
let task = Task<Progress, String, NSError> { (progress, fulfill, reject, configure) in

    Alamofire.download(.GET, "http://httpbin.org/stream/100", destination: somewhere)
    .progress { (bytesWritten, totalBytesWritten, totalBytesExpectedToWrite) in

        progress((bytesWritten, totalBytesWritten, totalBytesExpectedToWrite) as Progress)

    }.response { (request, response, data, error) in

        if let error = error {
            reject(error)
            return
        }

        fulfill("OK")

    }

    return
}

// set progress & then
task.progress { progress in

    println("\(progress.bytesWritten)")
    println("\(progress.totalBytesWritten)")
    println("\(progress.totalBytesExpectedToWrite)")

}.then { (value: String) -> Void in
    // do something with fulfilled value
}

For more examples, please see XCTest cases.

API Reference

Task.init(closure:)

Define your task inside closure.

let task = Task<Float, NSString?, NSError> { (progress, fulfill, reject, configure) in

    player.doSomethingWithCompletion { (value: NSString?, error: NSError?) in
        if error == nil {
            fulfill(value)
        }
        else {
            reject(error)
        }
    }
}

In order to pipeline future task.value or task.errorInfo (tuple of (error: Error?, isCancelled: Bool)) via then and catch methods, you have to call fulfill(value) and reject(error) inside closure.

Optionally, you can call progress(progressValue) multiple times before calling fulfill/reject to transfer progressValue outside of the closure, notifying it to task itself.

To add pause/resume/cancel functionality to your task, use configure to wrap up the original one.

// NOTE: use weak to let task NOT CAPTURE player via configure
configure.pause = { [weak player] in
    if let p = player { p.pause() }
}
configure.resume = { [weak player] in
    if let p = player { p.resume() }
}
configure.cancel = { [weak player] in
    if let p = player { p.cancel() }
}

task.progress(_ progressClosure:) -> task

task.progress { (progressValue: Progress) in
    println(progressValue)
    return
}.then { ... }

task.progress(progressClosure) will add progressClosure to observe progressValue which is notified from inside previous init-closure. This method will return same task, so it is useful to chain with forthcoming then and catch.

task.then(_ closure:) -> newTask

task.then(closure) will return a new task which behaves differently depending on what kind of closure is passed in.

  1. closure used for fulfilled only
  2. closure used for both fulfilled & rejected

1. closure used for fulfilled only = fulfilledClosure

fulfilledClosure will be invoked only when task is only fulfilled.

This case is similar to JavaScript's promise.then(onFulfilled).

  • fulfilledClosure: Value -> Value2 (flow: task => newTask)

    // task will be fulfilled with value "Hello"

task.then { (value: String) -> String in
    return "\(value) World"  // string value returns new string
}.then { (value: String) -> Void in
    println("\(value)")  // Hello World
    return"
}

  • fulfilledClosure: Value -> Task (flow: task => task2 => newTask)

    // task will be fulfilled with value "Hello"
// task2 will be fulfilled with value "\(value) Swift"

task.then { (value: String) -> Task<Float, String, NSError> in
    let task2 = ... // fulfilling "\(value) Swift"
    return task2
}.then { (value: String) -> Void in
    println("\(value)")  // Hello Swift
    return"
}

2. closure for both fulfilled & rejected = thenClosure

In this case, thenClosure will be invoked when task is either fulfilled or rejected. This means, thenClosure is mostly called in future compared to fulfilledClosure, which is invoked only when fulfilled.

This case is similar to JavaScript's promise.then(onFulfilled, onRejected).

  • thenClosure: (Value?, ErrorInfo?) -> Value2 (flow: task => newTask)

    // task will be fulfilled with value "Hello"

task.then { (value: String?, errorInfo: ErrorInfo?) -> String in
    // nil-check to find out whether task is fulfilled or rejected
    if errorInfo == nil {
        return "\(value) World"  // string value returns new string
    }
    else {
        return "\(value) Error"
    }
}.then { (value: String) -> Void in
    println("\(value)")  // Hello World
    return"
}

  • thenClosure: (Value?, ErrorInfo?) -> Task (flow: task => task2 => newTask)

    // task will be fulfilled with value "Hello"
// task2 will be fulfilled with value "\(value) Swift"

task.then { (value: String) -> Task<Float, String, NSError> in
    if errorInfo == nil {
        let task2 = ... // fulfilling "\(value) Swift"
        return task2
    }
    else {
        return someOtherTask
    }
}.then { (value: String) -> Void in
    println("\(value)")  // Hello Swift
    return"
}

task.catch(_ catchClosure:) -> newTask

Similar to task.then(fulfilledClosure) for fulfilled only, task.catch(catchClosure) will invoke catchClosure only when task is either rejected or cancelled.

This case is similar to JavaScript's promise.then(undefined, onRejected) or promise.catch(onRejected).

// task will be rejected with error "Oh My God"

task.then { (value: String) -> Void in
    println("\(value)") // never reaches here
    return
}.catch { (error: NSError?, isCancelled: Bool) -> Void in
    println("\(error!)")  // Oh My God
    return
}

Task.all(_ tasks:) -> newTask

Task.all(tasks) is a new task that performs all tasks simultaneously and will be:

  • fulfilled when all tasks will be fulfilled
  • rejected when any of the task will be rejected

Task.any(_ tasks:) -> newTask

Task.any(tasks) is an opposite of Task.all(tasks) which will be:

  • fulfilled when any of the task will be fulfilled
  • rejected when all tasks will be rejected

Task.some(_ tasks:) -> newTask

Task.some(tasks) is a new task that performs all tasks without internal rejection, and is fulfilled with given tasks's fulfilled values. Note that this new task will also become fulfilled with empty value-array, even though all tasks are rejected.

Related Articles

Licence

MIT