Draw circle with hole by using MKOverlayRenderer does not work well - ios

Question

I'd like to draw circle with hole (like donut) on mapview.
my code is here.
- (void)drawMapRect:(MKMapRect)mapRect zoomScale:(MKZoomScale)zoomScale inContext:(CG ContextRef)context {
WPCircleOverlay * circleOverlay = self.overlay;
CGPoint centerPoint = [self pointForMapPoint:MKMapPointForCoordinate(circleOverlay.coordinate)];
CGFloat innerRadius = MKMapPointsPerMeterAtLatitude(circleOverlay.coordinate.latitude) * circleOverlay.innerRadius;
CGFloat outerRadius = MKMapPointsPerMeterAtLatitude(circleOverlay.coordinate.latitude) * circleOverlay.outerRadius;
CGMutablePathRef path = CGPathCreateMutable();
//CGPathMoveToPoint(path, ...);
CGPathAddArc(path, NULL, centerPoint.x, centerPoint.y, outerRadius, 0, 2 * M_PI, true);
CGPathCloseSubpath(path);
// Add the inner arc to the path (later used to substract the inner area)
CGPathAddArc(path, NULL, centerPoint.x, centerPoint.y, innerRadius, 0, 2 * M_PI, true);
CGPathCloseSubpath(path);
// Add the path to the context
CGContextAddPath(context, path);
CGContextSetFillColorWithColor(context, self.fillColor.CGColor);
CGContextEOFillPath(context);
CGPathRelease(path);
It works well in simulator, but on device it doesn't.
On device, outer circle is filled with color, and inner circle wasn't clipped.
How can I modify my code to work well on device?

Answer 1

I fixed it by using CGContextAddEllipseInRect method instead of CGContextAddArc.
WPCircleOverlay * circleOverlay = self.overlay;
CGRect rectForMapRect = [self rectForMapRect:mapRect];
CGPoint centerPoint = [self pointForMapPoint:MKMapPointForCoordinate(circleOverlay.coordinate)];
CGFloat innerRadius = MKMapPointsPerMeterAtLatitude(circleOverlay.coordinate.latitude) * circleOverlay.innerRadius;
CGFloat outerRadius = MKMapPointsPerMeterAtLatitude(circleOverlay.coordinate.latitude) * circleOverlay.outerRadius;
CGRect innerRect = CGRectMake(centerPoint.x - innerRadius, centerPoint.y - innerRadius, innerRadius * 2.0, innerRadius * 2.0);
CGRect outerRect = CGRectMake(centerPoint.x - outerRadius, centerPoint.y - outerRadius, outerRadius * 2.0, outerRadius * 2.0);
if (CGRectIntersectsRect(rectForMapRect, outerRect)) {
CGContextAddRect(context, rectForMapRect);
CGContextSaveGState(context);
CGContextClip(context);
CGContextAddEllipseInRect(context, outerRect);
CGContextAddEllipseInRect(context, innerRect);
CGContextSaveGState(context);
CGContextEOClip(context);
UIColor * color = [self.fillColor copy];
CGContextSetFillColorWithColor(context, color.CGColor);
CGContextFillRect(context, outerRect);
CGContextRestoreGState(context);
CGContextRestoreGState(context);
UIGraphicsPopContext();
}