RxSwift and CLLocation : crash when trying to get user location

Question

I am using RSwift library in my app. I am trying to get the user location in order to send it in a network request. To get this location, I need to use Observables because the function must throw an error in case of user did not authorize location.

This algorithm is a part of a concatenated array of many Observables ran in an another thread than the main thread (in order to not freeze the UI). I need to execute the "get user location" function in the main thread because if not executed in the main thread it crash and the crash log is :

fatal error: Executing on backgound thread. Please use `MainScheduler.instance.schedule` to schedule work on main thread

In the above code, there is the geolocation helper init (this is a singleton) and the method executed to get the user location (or an error).

private var authorized: Observable<Bool?>
private var location: Observable<CLLocationCoordinate2D>
private let locationManager = CLLocationManager()

private init() {
    locationManager.desiredAccuracy = LocationOptions.desiredAccuracy

    authorized = Observable.just(false)
        .map({ _ in CLLocationManager.authorizationStatus() })
        .concat(locationManager.rx_didChangeAuthorizationStatus)
        .distinctUntilChanged()
        .map({ authorizedStatus in
            switch authorizedStatus {
            case .AuthorizedAlways, .AuthorizedWhenInUse:
                return true
            case .NotDetermined:
                return nil
            case .Restricted, .Denied:
                return false
            }
        })
        .catchErrorJustReturn(false)

    location = locationManager.rx_didUpdateLocations
        .filter { $0.count > 0 }
        .map({ return $0.last!.coordinate })
}


func getLocation() -> Observable<Location> {
    return authorized
        .flatMap({ authorized -> Observable<CLLocationCoordinate2D> in
            guard let authorized = authorized else {
                self.locationManager.requestAlwaysAuthorization()
                return Observable.empty()
            }

            if authorized {
                self.startUpdating()
                return self.location
            } else {
                return Observable.error(
                    NSError(
                        domain:"",
                        code: 0,
                        userInfo:nil )
                )
            }
        })
        // We just need one position updated
        .take(1)
        .map({ coordinate in
            self.stopUpdating()

            let location = Location(longitude: coordinate.longitude, latitude: coordinate.latitude, latestUpdatedDate: NSDate())
            if location.isValid() {
                saveLocation(location)
            }
            return location
        })
        .doOnError({ error in self.stopUpdating() })
}

I see in the RXSwift geolocation example ( https://github.com/ReactiveX/RxSwift/pull/429 ) a class that can handle it with Drivers but I really need to have an error and Drivers cannot return errors.

I would appreciate if someone can help me on how to achieve this.

I already tried to add " .observeOn(MainScheduler.instance) " to the 2 observables but it freezes the UI.. maybe there is a better way to do this without freezing UI.

Thanks

Answer 1

@romroll, DelegateProxy works only on Main thread in RxCocoa for now. Try to do something like this

.map({ _ in CLLocationManager.authorizationStatus() })
        .observeOn(MainScheduler.instance)
        .concat(locationManager.rx_didChangeAuthorizationStatus)
        .observeOn(someOtherScheduler)
        .distinctUntilChanged()

Hope, this helps. If not, you can always reach me in the RxSwiftSlack , by mentioning @sergdort, or somebody else :)

Answer 2

您必须将扩展CLLocationManager + Rx.swift和RxCLLocationManagerDelegateProxy.swift复制到您的项目，因为它不再是RxCocoa的一部分