swift - 使用 flatMapLatest 合并两个流

Question

在与 flatMapLatest 中的 observables 结合时遇到问题

逻辑:在每个事件的下一个事件上，我想将它与下一个 getCurrentLocation 事件结合在一起，该事件发生在 activityEvent 被触发之后，将它们连接在一个元组中然后用它做点什么。

目前是这样

ActivitiesController
    .start()
    .flatMapLatest { activity in 
        LocationController.shared.getCurrentLocation().map { ($0, activity) }
    }
    .subscribe(onNext: { (activity, currentLocation in
        print("")
    })
    .disposed(by: disposeBag)

位置代码:

func getCurrentLocation() -> Observable<CLLocation> {
    self.requestLocationUseAuthorizationIfNotDetermined(for: .always)
    self.locationManager.requestLocation()
    return self.publishSubject.take(1) // take next object from the publish subject (only one)
}

func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    guard let location = locations.last, location.horizontalAccuracy > 0 else {
        return
    }
    self.publishSubject.onNext(location)
}

因为我们知道 requestLocation() 会触发 didUpdateLocations，所以我们认为逻辑应该起作用，但它没有起作用

结果是 locationManager 并不总是更新和返回旧值而不是新值

你们有什么想法吗？

Answer 1

您需要使用 withLatestFrom 而不是 flatMapLatest。

LocationController.shared.getCurrentLocation().withLatestFrom(activityEvent) {
    // in here $0 will refer to the current location that was just emitted and
    // $1 will refer to the last activityEvent that was emitted.
    return ($0, $1)
}