RxSwift - Determining whether an Observable has been disposed - ios

Question

I'm trying to get Publisher which vends Observables to its clients Consumer, to determine when one of its consumers has disposed of its Observable.
Annoyingly. my code was working fine, until I removed an RxSwift .debug from within the Consumer code.
Is there some alternative way I might get this working?
private class Subscriber {
var ids: [Int]
// This property exists so I can watch whether the observable has
// gone nil (which I though would happen when its been disposed, but it
// seems to happen immediately)
weak var observable: Observable<[Updates]>?
}
class Publisher {
private let relay: BehaviorRelay<[Int: Updates]>
private var subscribers: [Subscriber] = []
func updatesStream(for ids: [Int]) -> Observable<[Updates]> {
let observable = relay
.map { map in
return map
.filter { ids.contains($0.key) }
.map { $0.value }
}
.filter { !$0.isEmpty }
.asObservable()
let subscriber = Subscriber(ids: ids, observable: observable)
subscribers.append(subscriber)
return observable
}
private func repeatTimer() {
let updates: [Updates] = ....
// I need to be able to determine at this point whether the subscriber's
// observable has been disposed of, so I can remove it from the list of
// subscribers. However `subscriber.observable` is always nil here.
// PS: I am happy for this to happen before the `repeatTimer` func fires
subscribers.remove(where: { subscriber in
return subscriber.observable == nil
})
relay.accept(updates)
}
}
class Client {
private var disposeBag: DisposeBag?
private let publisher = Publisher()
func startWatching() {
let disposeBag = DisposeBag()
self.disposeBag = disposeBag
publisher
// with the `.debug` below things work OK, without it the
///`Publisher.Subscriber.observable` immediately becomes nil
//.debug("Consumer")
.updatesStream(for: [1, 2, 3])
.subscribe(onNext: { values in
print(values)
})
.disposed(by: disposeBag)
}
func stopWatching() {
disposeBag = nil
}
}

Answer 1

I think this is a very bad idea, but it solves the requested problem... If I had to put this code in one of my projects, I would be very worried about race conditions...
struct Subscriber {
let ids: [Int]
var subscribeCount: Int = 0
let lock = NSRecursiveLock()
}
class Publisher {
private let relay = BehaviorRelay<[Int: Updates]>(value: [:])
private var subscribers: [Subscriber] = []
func updatesStream(for ids: [Int]) -> Observable<[Updates]> {
var subscriber = Subscriber(ids: ids)
let observable = relay
.map { map in
return map
.filter { ids.contains($0.key) }
.map { $0.value }
}
.filter { !$0.isEmpty }
.do(
onSubscribe: {
subscriber.lock.lock()
subscriber.subscribeCount += 1
subscriber.lock.unlock()
},
onDispose: {
subscriber.lock.lock()
subscriber.subscribeCount -= 1
subscriber.lock.unlock()
})
.asObservable()
subscribers.append(subscriber)
return observable
}
private func repeatTimer() {
subscribers.removeAll(where: { subscriber in
subscriber.subscribeCount == 0
})
}
}