在iOS 8上清除MKMapView内存

Question

每当初始化MKMapView并将其设置为某个位置

- (void) setMapLocationItem:(Location*)geofence{

    if(self.mapView==nil){
        self.mapView = [[MKMapView alloc] initWithFrame:self.view.bounds];
        [self.mapView setDelegate:self];
        [self.view addSubview:self.mapView];
        [self.view sendSubviewToBack:self.mapView];
        [self.view sendSubviewToBack:self.collectionView];
    }
    [self.mapView setHidden:NO];
    [_mapView removeAnnotations:_mapView.annotations];
    CLLocationCoordinate2D coordinate;

        coordinate= CLLocationCoordinate2DMake(geofence.latitude.doubleValue, geofence.longitude.doubleValue);

    CGFloat radius = 110;
    if([geofence.radius boolValue])
        radius = [geofence.radius floatValue];
    MKCoordinateRegion region = MKCoordinateRegionMakeWithDistance (coordinate, radius, radius);
    [_mapView setRegion:region animated:NO];

    self.annotation = [[MKPointAnnotation alloc] init];
    self.annotation.coordinate = coordinate;
    self.annotation.title = geofence.name;
    self.annotation.subtitle = geofence.address;
    [_mapView addAnnotation:self.annotation];
}

每当viewController关闭时，我使用的内存都不会被释放。

只有在初始化另一个MKMapView时才会释放它。任何想法也是为什么这是？ 我在这个问题iOS6 MKMapView Memory Issue

中提到了解决方案