How can i convert NSBezierPath to CGPath

Right from Apple documentation: Creating a CGPathRef From an NSBezierPath Object

Here is the relevant code.

@implementation NSBezierPath (BezierPathQuartzUtilities)
// This method works only in OS X v10.2 and later.
- (CGPathRef)quartzPath
{
    int i, numElements;

    // Need to begin a path here.
    CGPathRef           immutablePath = NULL;

    // Then draw the path elements.
    numElements = [self elementCount];
    if (numElements > 0)
    {
        CGMutablePathRef    path = CGPathCreateMutable();
        NSPoint             points[3];
        BOOL                didClosePath = YES;

        for (i = 0; i < numElements; i++)
        {
            switch ([self elementAtIndex:i associatedPoints:points])
            {
                case NSMoveToBezierPathElement:
                    CGPathMoveToPoint(path, NULL, points[0].x, points[0].y);
                    break;

                case NSLineToBezierPathElement:
                    CGPathAddLineToPoint(path, NULL, points[0].x, points[0].y);
                    didClosePath = NO;
                    break;

                case NSCurveToBezierPathElement:
                    CGPathAddCurveToPoint(path, NULL, points[0].x, points[0].y,
                                        points[1].x, points[1].y,
                                        points[2].x, points[2].y);
                    didClosePath = NO;
                    break;

                case NSClosePathBezierPathElement:
                    CGPathCloseSubpath(path);
                    didClosePath = YES;
                    break;
            }
        }

        // Be sure the path is closed or Quartz may not do valid hit detection.
        if (!didClosePath)
            CGPathCloseSubpath(path);

        immutablePath = CGPathCreateCopy(path);
        CGPathRelease(path);
    }

    return immutablePath;
}
@end

Bug Reporter

rdar://15758302: NSBezierPath to CGPath.

For macOS better use - CGMutablePath

But, if you want cgPath for NSBezierPath:

Swift 5.0

extension NSBezierPath {

  var cgPath: CGPath {
    let path = CGMutablePath()
    var points = [CGPoint](repeating: .zero, count: 3)
    for i in 0 ..< self.elementCount {
      let type = self.element(at: i, associatedPoints: &points)

      switch type {
      case .moveTo:
        path.move(to: points[0])

      case .lineTo:
        path.addLine(to: points[0])

      case .curveTo:
        path.addCurve(to: points[2], control1: points[0], control2: points[1])

      case .closePath:
        path.closeSubpath()

      @unknown default:
        break
      }
    }
    return path
  }
}

c# Xamarin

        private CGPath convertNSBezierPathToCGPath(NSBezierPath sourcePath)
    {
        CGPath destinationPath = new CGPath();

        int i, numElements;

        // Then draw the path elements.
        numElements = (int)Convert.ToInt64(sourcePath.ElementCount);

        if (numElements > 0)
        {

            CGPath path = new CGPath();
            CGPoint[] points;
            bool didClosePath = true;

            for (i = 0; i < numElements; i++)
            {
                switch (sourcePath.ElementAt(i, out points))
                {
                    case NSBezierPathElement.MoveTo:
                        path.MoveToPoint(points[0]);
                        break;


                    case NSBezierPathElement.LineTo:
                        path.MoveToPoint(points[0]);
                        didClosePath = false;
                        break;

                    case NSBezierPathElement.CurveTo:
                        path.AddCurveToPoint(cp1: points[0], cp2: points[1], points[2]);
                        didClosePath = false;
                        break;

                    case NSBezierPathElement.ClosePath:
                        path.CloseSubpath();
                        didClosePath = true;
                        break;
                }
            }

            if (!didClosePath)
                path.CloseSubpath();

            destinationPath = new CGPath(path);

        }

        return destinationPath;

}