Limiting concurrent access to a service class with RxSwift

Question

Given a service class like this:

class Service {
    let networkService = NetworkService()

    func handleJobA(input: String) -> Observable

        

Answer 1

You need a serial Scheduler that is dedicated to that service. Here is an example that can be pasted to a playground:

/// playground

import RxSwift

class Service {

    func handleJobA(input: String) -> Observable<String> {

        return Observable.create { observer in
            print("start job a")
            sleep(3)
            observer.onNext(input)
            print("complete job a")
            observer.onCompleted()
            return Disposables.create()
        }.subscribeOn(scheduler)
    }

    func handleJobB(input: String) -> Observable<String> {
        return Observable.create { observer in
            print("start job b")
            sleep(3)
            observer.onNext(input)
            print("complete job b")
            observer.onCompleted()
            return Disposables.create()
            return Disposables.create()
        }.subscribeOn(scheduler)
    }

    let scheduler = SerialDispatchQueueScheduler(internalSerialQueueName: "Service")
}


let service = Service()

_ = Observable.from(["hello","world","swift"])
    .flatMap { service.handleJobA(input: $0) }
    .subscribe(onNext:{
        print("result " + $0)
    })

_ = Observable.from(["hello","world","swift"])
    .flatMap { service.handleJobB(input: $0) }
    .subscribe(onNext:{
        print("result " + $0)
    })

import PlaygroundSupport

PlaygroundPage.current.needsIndefiniteExecution = true

Answer 2

maybe you want concat operator,i wrote some test codes below see if this you want :

 func sleepAndPrint(label:String) -> Observable<String> {


        return Observable.create { obser -> Disposable in
            DispatchQueue.global().async {
                sleep(3)
                print("\(label) come")
                obser.onNext(label)
                obser.onCompleted()
            }

            return Disposables.create()
        }
    }


Observable.from(["hello","world","swift"])
    // we need observable of observable sequences so just use map
    // Observable<Observable<String>> in this case
    .map{
        sleepAndPrint(label: $0)
    }
    // Concatenates all inner observable sequences, as long as the previous observable sequence terminated successfully.
    .concat()

    .subscribe(onNext:{
        print("subscribe: " + $0)
    })
    .addDisposableTo(disposeBag)

    prints : 
      hello come
      subscribe: hello
      world come
      subscribe: world
      swift come
      subscribe: swift