MKMapView内存问题

override func viewDidLoad() {
    super.viewDidLoad()
    mapView.delegate = self
}

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    mapView.removeAnnotations(mapView.annotations)
}

func mapView(_ mapView: MKMapView, viewFor annotation: MKAnnotation) -> MKAnnotationView? {
    if let annotationView = mapView.dequeueReusableAnnotationView(withIdentifier: "AnnotationView") {
        annotationView.annotation = annotation
        return annotationView
    } else {
        let annotationView = MKAnnotationView(annotation: annotation, reuseIdentifier: "AnnotationView")
        annotationView.canShowCallout = true
        return annotationView
    }
}

let mapCache = MKTileOverlayRenderer.TileCache()
mapCache.capacity = 100 // 设置缓存容量