Polling for a async task and then waiting for either 1 success or all response rejected

Question

PromiseKit version: 4.0

Xcode version: 8.3.2

I have recently started using PromiseKit.

Actually, I am creating a polling HTTP request which in returns gives "completed" or "notCompleted".

I have to keep making HTTP calls after every 1 secs for a duration of 5 seconds.

What I need to achieve is if any 1 call gives me completed status I will return fulfilled("completed"). But if all of my requests gives me a response of "notCompleted", I need to return reject("notCompleted")

return Promise<T> { fulfilled, reject
let timer1 =  Timer.scheduledTimer(withTimeInterval: TimeInterval(1), repeats: true) { timer in
    pArr.append(Promise<T> { f, r in

        doSomeAsyncTask { T in
            if success {
                f(T)
                fulfilled(T)
                timer.invalidate()
            } else {
                 r(ErrorNotCompleted)
            }
        }

        // timeout option
        _ = after(interval: TimeInterval(15)).then(execute: { () -> Void in
            reject(timeoutForConfirmation)
        })
    })
    }


Timer.scheduledTimer(withTimeInterval: TimeInterval(5), repeats: false) { timer in
    timer1.invalidate()
    timer.invalidate()
    when(resolved: pArr).then { results in
        let count = results.filter({ result -> Bool in
             return result.boolValue
        }).count

        if count == 0 {
            // TODO: then reject here
            reject(ErrorNotCompleted)
        }

        }.catch { error in
            print(error)
    }
}

} 
timer1.fire()

How can I achieve this?

Is there a better way to write the above code in PromiseKit.

score 1 · Accepted Answer · answered May 29 '17 at 03:27

Here is a way to do a basic loop with Promises... It's from my gist: https://gist.github.com/dtartaglia/2b19e59beaf480535596

I think all you would need to do is make sure your promise producer (body) has a suitable delay in it before making the network call.

/**
Repeadetly evaluates a promise producer until a value satisfies the predicate.
`promiseWhile` produces a promise with the supplied `producer` and then waits
for it to resolve. If the resolved value satifies the predicate then the
returned promise will fulfill. Otherwise, it will produce a new promise. The
method continues to do this until the predicate is satisfied or an error occurs.
- Returns: A promise that is guaranteed to fulfill with a value that satisfies
the predicate, or reject.
*/

func promiseWhile<T>(pred: (T) -> Bool, body: () -> Promise<T>, fail: (() -> Promise<Void>)? = nil) -> Promise<T> {
    return Promise { fulfill, reject in
        func loop() {
            body().then { (t) -> Void in
                if !pred(t) { fulfill(t) }
                else {
                    if let fail = fail {
                        fail().then { loop() }
                        .error { reject($0) }
                    }
                    else { loop() }
                }
            }
            .error { reject($0) }
        }
        loop()
    }
}

Polling for a async task and then waiting for either 1 success or all response rejected

1 Answers1