RXSwift why loading variable return wrong value? - rx-swift

Question

Here is my view model:
let loadMoreTrigger = PublishSubject<Void>()
let refreshTrigger = PublishSubject<Void>()
let loading = BehaviorRelay<Bool>(value: false)
let stories = BehaviorRelay<[Story]>(value: [])
var offset = 0
let error = PublishSubject<String>()
let selectedFeedType: BehaviorRelay<FeedType> = BehaviorRelay(value: .best)
override init() {
super.init()
let refreshRequest = loading.asObservable().sample(refreshTrigger).flatMap { loading -> Observable<[Story]> in
if loading {
return Observable.empty()
} else {
self.offset = 0
return self.fetchStories(type: self.selectedFeedType.value, offset: self.offset)
}
}
let loadMoreRequest = loading.asObservable().sample(loadMoreTrigger).flatMap { loading -> Observable<[Story]> in
if loading {
return Observable.empty()
} else {
self.offset += 10
return self.fetchStories(type: self.selectedFeedType.value, offset: self.offset)
}
}
let request = Observable.merge(refreshRequest, loadMoreRequest).share(replay: 1)
let response = request.flatMap { (stories) -> Observable<[Story]> in
request.do(onError: { error in
self.error.onNext(error.localizedDescription)
}).catchError { (error) -> Observable<[Story]> in
Observable.empty()
}
}.share(replay: 1)
Observable.combineLatest(request, response, stories.asObservable()) { request, response, stories in
return self.offset == 0 ? response : stories + response
}.sample(response).bind(to: stories).disposed(by: disposeBag)
Observable.merge(request.map{_ in true}, response.map{_ in false}, error.map{_ in false}).bind(to: loading).disposed(by: disposeBag)
}
Then when i checking loading observer i have false -> true, instead of true -> false. I just don't understand why it happening.
loading.subscribe {
print($0)
}.disposed(by: disposeBag)
In my viewController i call refreshTrigger on viewWillAppear using rx.sentMessage
Here is getFeed function:
func getFeed(type: FeedType, offset: Int) -> Observable<[Story]> {
return provider.rx.request(.getFeed(type: type, offset: offset)).asObservable().flatMap { (response) -> Observable<[Story]> in
do {
let feedResponse = try self.jsonDecoder.decode(BaseAPIResponse<[Story]>.self, from: response.data)
guard let stories = feedResponse.data else { return .error(APIError.requestFailed)}
return .just(stories)
} catch {
return .error(error)
}
}.catchError { (error) -> Observable<[Story]> in
return .error(error)
}
}

Answer 1

Your request and response observables are emitting values at the exact same time. Which one shows up in your subscribe first is undefined.
Specifically, request doesn't emit a value until after the fetch request completes. Try this instead:
Observable.merge(
loadMoreTrigger.map { true },
refreshTrigger.map { true },
response.map { _ in false },
error.map { _ in false }
)
.bind(to: loading)
.disposed(by: disposeBag)
There are lots of other problems in your code but the above answers this specific question.