GoogleMapProvider.kt

class GoogleMapProvider: MapProvider {
  private val mapCache: BehaviorSubject<Map> = BehaviorSubject.createDefault(DEFAULT)

  override fun initMap(): Observable<Map> {
      return Observable.create(this::addMapFragment)
          .switchMapSingle(this::waitingForLoading)
          .doOnNext(mapCache::onNext)
  }

  override fun getMap(): Observable<Map> = mapCache.hide()
}