by Adding Polyline(path) on MKMapview crashing the app in ios6 - ios6

Question

I have a requirement to adding a path in my MKMapview between two annotation pin. There is no issue with ios 5 or older but when i try to run app in ios 6 app is surprisingly quit. below is my code. If there is any correction in my code then please suggest me.
1.So my question is suggest the best way how to decrees memory in my following code so that i can solve crash in my Application.
- (void)viewDidLoad
{
NVPolylineAnnotation *annotation = [[NVPolylineAnnotation alloc] initWithPoints:pathArray mapView:_mapView];
[_mapView addAnnotation:annotation];
[annotation release];
[pathArray removeAllObjects];
}
- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation
{
NSLog(#"%s",__FUNCTION__);
if ([annotation isKindOfClass:[NVPolylineAnnotation class]])
{
NSLog(#"=========ANOTATION=========NVPolylineAnnotationView START");
//ann=[ann initWithAnnotation:annotation mapView:_mapView];
NVPolylineAnnotationView *ann=[[NVPolylineAnnotationView alloc] init];
return [[ann initWithAnnotation:annotation mapView:_mapView] autorelease];//[[[NVPolylineAnnotationView alloc] initWithAnnotation:annotation mapView:_mapView] autorelease];
}
else if([annotation isKindOfClass:[MapViewAnnotation class]])
{
MKPinAnnotationView *annView=[[MKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:#"pointers"] ;
// annView.rightCalloutAccessoryView = [UIButton buttonWithType: UIButtonTypeDetailDisclosure];
annView.animatesDrop=NO;
annView.canShowCallout = TRUE;
return [annView autorelease];
}
else if([annotation isKindOfClass:[PlacePin class]])
{
{
MKPinAnnotationView *pinView = nil;
if(annotation != mapView.userLocation)
{
static NSString *defaultPinID = #"com.invasivecode.pin";
pinView = (MKPinAnnotationView *)[mapView dequeueReusableAnnotationViewWithIdentifier:defaultPinID];
if ( pinView == nil )
pinView = [[[MKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:defaultPinID] autorelease];
pinView.pinColor = MKPinAnnotationColorGreen;
pinView.canShowCallout = YES;
pinView.animatesDrop = NO;
}
else {
[mapView.userLocation setTitle:#"I am here"];
}
return pinView;
}
}
return nil;
}
- (void) mapView:(MKMapView *)mapView didAddAnnotationViews:(NSArray *)views
{
NSLog(#"%s",__FUNCTION__);
// fixes that some marker are behind the polyline
for (int i=0; i<[views count]; i++)
{
MKAnnotationView *view = [views objectAtIndex:i];
if ([view isKindOfClass:[NVPolylineAnnotationView class]])
{
[[view superview] sendSubviewToBack:view];
/* In iOS version above 4.0 we need to update the polyline view after it
has been added to the mapview and it ready to be displayed. */
NSString *reqSysVer = #"4.0";
NSString *currSysVer = [[UIDevice currentDevice] systemVersion];
if ([currSysVer compare:reqSysVer options:NSNumericSearch] != NSOrderedAscending)
{
[self updatePolylineAnnotationView];
}
}
}
NSLog(#"----------didAddAnnotationViews");
}
- (void)updatePolylineAnnotationView
{
NSLog(#"%s",__FUNCTION__);
MKAnnotationView *annotationView = [views objectAtIndex:0];
id <MKAnnotation> mp = [annotationView annotation];
[mapView selectAnnotation:mp animated:NO];
*/
for (NSObject *a in [_mapView annotations])
{
if ([a isKindOfClass:[NVPolylineAnnotation class]])
{
NVPolylineAnnotation *polyline = (NVPolylineAnnotation *)a;
NSObject *pv = (NSObject *)[_mapView viewForAnnotation:polyline];
if ([pv isKindOfClass:[NVPolylineAnnotationView class]])
{
NVPolylineAnnotationView *polylineView =
(NVPolylineAnnotationView *)[_mapView viewForAnnotation:polyline];
[polylineView regionChanged];
}
}
}
}