Как перестать вызывать определенную строку кода в Google Maps в iOS Objective c?

Question

Это мой код ...

- (void)mapView:(GMSMapView *)mapView idleAtCameraPosition:(GMSCameraPosition *)position {

_a2bBooking.pickupLocation = position.target;
if (position.target.latitude != 0.0)
    [self getNearbyVehiclesForLocation:_a2bBooking.userLocation pickupLocation:_a2bBooking.pickupLocation];

}

Этот метод вызывается несколько раз ...

-(void) getNearbyVehiclesForLocation: (CLLocationCoordinate2D)userOrigin pickupLocation:(CLLocationCoordinate2D)pickupOrigin {

_alertView = [BRUtility showLoadingMessageWithTitle:@"Loading" delegate:self];

NSString *anURLString = [NSString stringWithFormat:@"%@%@?userlat=%f&userLng=%f&pickupLat=%f&pickupLng=%f",kSmartCommuteBaseURL,kGetNearbyVehiclesURL,_a2bBooking.userLocation.latitude,_a2bBooking.userLocation.longitude,_a2bBooking.pickupLocation.latitude,_a2bBooking.pickupLocation.longitude];

AFHTTPSessionManager *manager = [BRUtility getAFHTTPSessionManager];

[manager GET:anURLString parameters:nil progress:nil success:^(NSURLSessionDataTask * _Nonnull task, id  _Nullable responseObject) {
    [BRUtility dismissLoader:self];
    NSString *anErrorCode = [responseObject valueForKey:@"errorCode"];
    if (anErrorCode.intValue == 0) {
        NSError *error = nil;
        self.nearbyVehicles = [MTLJSONAdapter modelsOfClass:[NearbyBikesResponse class] fromJSONArray:[[responseObject valueForKey:@"data"] valueForKey:@"nearbyVehicleList"] error:&error];
        [self.mapView clear];
        for (NearbyBikesResponse *nearbyVehicle in self.nearbyVehicles) {
            [self addMarker:nearbyVehicle];
        }
        [self zoomToFit];
    }
    else {
        self.nearbyVehicles = [[NSArray alloc] init];
    }
} failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error) {
    [BRUtility dismissLoader:self];
    [BRUtility showErrorMessageWithTitle:@"Error" message:@"Please try again!" delegate:self];
}];
 }

Этот метод вызывается несколько раз,Я хочу вызвать этот метод только один раз.Как перестать звонить несколько раз?