gistfile1.swift

extension NSBezierPath {
    var CGPath: CGMutablePath! {
        get {
            if self.elementCount == 0 {
                return nil
            }
            
            let path = CGPathCreateMutable()
            var didClosePath = false
            
            for i in 0..<self.elementCount {
                var points:[NSPoint] = [NSPoint](count: 3, repeatedValue: NSZeroPoint)
                
                switch self.elementAtIndex(i, associatedPoints: &points) {
                case .MoveToBezierPathElement:
                    CGPathMoveToPoint(path, nil, points[0].x, points[0].y)
                case .LineToBezierPathElement:
                    CGPathAddLineToPoint(path, nil, points[0].x, points[0].y)
                case .CurveToBezierPathElement:
                    CGPathAddCurveToPoint(path, nil, points[0].x, points[0].y, points[1].x, points[1].y, points[2].x, points[2].y)
                case .ClosePathBezierPathElement:
                    CGPathCloseSubpath(path)
                    didClosePath = true
                }
            }
            
            if !didClosePath {
                CGPathCloseSubpath(path)
            }
            
            return CGPathCreateMutableCopy(path)
        }
    }
}

//Now you can:
class TerrainLayer: CALayer {
    override func drawInContext(ctx: CGContext!) {
        let path = NSBezierPath(roundedRect: bounds, xRadius:10, yRadius:10).CGPath
        
        CGPathAddRect(path, nil, bounds)
        CGContextSetFillColorWithColor(ctx, NSColor.redColor().CGColor)
        CGContextAddPath(ctx, path)
        CGContextFillPath(ctx)
    }
}