RxSwift

Rx.swift

// Retry with backoff
// Adapted from http://blog.danlew.net/2016/01/25/rxjavas-repeatwhen-and-retrywhen-explained/
Observable
    .range(start: 1, count: 10)
    .doOn(onNext: { i in
        if i == 5 {
            throw NSError(domain: "com.example", code: 1, userInfo: ["any": "thing"])
        }
    })
    .retryWhen { (attempts: Observable<ErrorType>) -> Observable<Int64> in
        attempts.doOn({ (event) -> Void in
            print("Attempt: \(attempts)")
        })

        return Observable
            .zip(attempts, Observable.range(start: 1, count: 3), resultSelector: { (o1, o2) in
                return o2
            })
            .flatMap({ i -> Observable<Int64> in
                print("Delay retry by \(i) seconds")
                return Observable.timer(RxTimeInterval(i), period: 0.0, scheduler: MainScheduler.instance)
            })
    }
    .distinctUntilChanged()
    .take(10)
    .subscribe { (event) in
        print("Event: \(event)")
    }