CountdownTimer.swift

import RxSwift

let Completed = NSError(domain: "Completed", code: 0, userInfo: nil)

class CountdownTimer {
    
    private let publisher = PublishSubject<Int>()
    private let signal: Observable<Int>
    
    init(_ count: Int) {
        signal =
            interleave([publisher,
                interval(1
                    , MainScheduler.sharedInstance)
                        //>- publish
                        >- take(count+1)
                        >- map { count - Int($0) }])
    }
    
    var observable: Observable<Int> { return signal }
    
    func sendCompleted() {
        publisher.on(.Completed)
    }

}

func interleave<E>(a: [Observable<E>]) -> Observable<E> {
    return from(a.map { concat([$0, failWith(Completed)]) })
        >- merge
        >- catch {
            $0 == Completed ? empty(): failWith($0)
        }
}

Can you please update. It would be helpful