ios 里如何判断当前应用的定位服务是否可用

if ([CLLocationManager locationServicesEnabled] &&
                ([CLLocationManager authorizationStatus] == kCLAuthorizationStatusAuthorized
                || [CLLocationManager authorizationStatus] == kCLAuthorizationStatusNotDetermined)) {
                //定位功能可用，开始定位
                _locationManger = [[CLLocationManager alloc] init];
                locationManger.delegate = self;
                [locationManger startUpdatingLocation];
            }
            else if ([CLLocationManager authorizationStatus] == kCLAuthorizationStatusDenied){
        NSlog("定位功能不可用，提示用户或忽略"); 
            }