Prevent MKPolygon to have knots - ios

Question

I'm developing an app with a map in which the user can draw a polygon area.
My issue is what it's possible drawing polygons with knots (see the image) (I don't know if knot is the right word). I didn't find a simply way preventing the polygon to get knots.
For the case of the attached image, I would like the small curl to be removed and even the outline to be smoothed
Do you know a way to make that?
The process of drawing the polygon while the user is touching the screen, does use MKPolyline, MKPolygon and MKOverlay as follows:
- (void)touchesBegan:(UITouch*)touch
{
CGPoint location = [touch locationInView:self.mapView];
CLLocationCoordinate2D coordinate = [self.mapView convertPoint:location toCoordinateFromView:self.mapView];
[self.coordinates addObject:[NSValue valueWithMKCoordinate:coordinate]];
}
- (void)touchesMoved:(UITouch*)touch
{
CGPoint location = [touch locationInView:self.mapView];
CLLocationCoordinate2D coordinate = [self.mapView convertPoint:location toCoordinateFromView:self.mapView];
[self.coordinates addObject:[NSValue valueWithMKCoordinate:coordinate]];
}
- (void)touchesEnded:(UITouch*)touch
{
CGPoint location = [touch locationInView:self.mapView];
CLLocationCoordinate2D coordinate = [self.mapView convertPoint:location toCoordinateFromView:self.mapView];
[self.coordinates addObject:[NSValue valueWithMKCoordinate:coordinate]];
[self didTouchUpInsideDrawButton:nil];
}
- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id <MKOverlay>)overlay
{
MKOverlayPathView *overlayPathView;
if ([overlay isKindOfClass:[MKPolygon class]])
{
// create a polygonView using polygon_overlay object
overlayPathView = [[MKPolygonView alloc] initWithPolygon:overlay];
overlayPathView.fillColor = [UIColor redColor];
overlayPathView.lineWidth = 1.5;
return overlayPathView;
}
else if ([overlay isKindOfClass:[MKPolyline class]])
{
overlayPathView = [[MKPolylineView alloc] initWithPolyline:(MKPolyline *)overlay];
overlayPathView.fillColor = [UIColor redColor];
overlayPathView.lineWidth = 3;
return overlayPathView;
}
return nil;
}

Answer 1

MKOverlayPathView was deprecated since iOS 7.0. You'd use MKOverlayRenderer instead of it and also related map delegate method.
Try to play with miterLimit property of MKOverlayRenderer.
Example:
-(MKOverlayRenderer *)mapView:(MKMapView *)mapView rendererForOverlay:(id<MKOverlay>)overlay {
if ([overlay isKindOfClass:[MKPolygon class]]) {
MKPolygonRenderer *polygonRenederer = [[MKPolygonRenderer alloc] initWithPolygon:overlay];
polygonRenederer.fillColor = [UIColor redColor];
polygonRenederer.lineWidth = 1.5;
polygonRenederer.miterLimit = 10;
return polygonRenederer;
} else if ([overlay isKindOfClass:[MKPolyline class]]) {
MKPolylineRenderer *lineRenderer = [[MKPolylineRenderer alloc] initWithPolyline:overlay];
lineRenderer.strokeColor = [UIColor redColor];
lineRenderer.lineWidth = 3;
return lineRenderer;
}
return nil;
}