iOS Multiple Polyline Overlay causes memory issue

Question

I’m using mkmapview in my application it contains multiple polyline overlay and multiple custom annotations, while running the application receiving memory warning oftenly, I struggled a lot

Thanks in advance.

for (int i = 0; i<[latArray count]-1; i++)
    {
        NSString *lat1 = [latArray objectAtIndex:i];
        NSString *longi1 = [longArray objectAtIndex:i];

        firstPlace = CLLocationCoordinate2DMake([lat1 doubleValue], [longi1 doubleValue]);

        NSString *lat2 = [latArray objectAtIndex:i+1];
        NSString *longi2 = [longArray objectAtIndex:i+1];

        secPlace = CLLocationCoordinate2DMake([lat2 doubleValue], [longi2 doubleValue]);

        [self directionRequest:firstPlace :secPlace index:i];
    }

-(void)directionRequest:(CLLocationCoordinate2D )firstCord :(CLLocationCoordinate2D )secCord index:(int)index
{

    @try
    {

        MKPlacemark *source=[[MKPlacemark alloc]initWithCoordinate:firstCord addressDictionary:[NSDictionary dictionaryWithObjectsAndKeys:@"",@"", nil]];

        MKMapItem *sourceMapItem=[[MKMapItem alloc]initWithPlacemark:source];
        [sourceMapItem setName:@""];

        MKPlacemark *destination=[[MKPlacemark alloc]initWithCoordinate:secCord addressDictionary:[NSDictionary dictionaryWithObjectsAndKeys:@"",@"", nil]];

        MKMapItem *destinationMapitem=[[MKMapItem alloc]initWithPlacemark:destination];
        [destinationMapitem setName:@""];

        MKDirectionsRequest *dirRequest=[[MKDirectionsRequest alloc]init];
        [dirRequest setSource:sourceMapItem];
        [dirRequest setDestination:destinationMapitem];
        //    dirRequest.requestsAlternateRoutes = YES;
        [dirRequest setTransportType:MKDirectionsTransportTypeAutomobile];

        MKDirections *direction=[[MKDirections alloc]initWithRequest:dirRequest];

        [direction calculateDirectionsWithCompletionHandler:^(MKDirectionsResponse *response, NSError *error)
         {

          //   NSLog(@"response = %@",response);
             NSArray *arrRoutes = [response routes];
             [arrRoutes enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop)
              {
                  MKRoute *rout = obj;
                  MKPolyline *line = [rout polyline];
                  [iMapView addOverlay:line];


              }];

         }];

    }
    @catch (NSException *exception)
    {

    }

}