Erasing lines in pdf context - swift

Question

I'm trying to generate a pdf of my UIView. In the view I can simply erase lines using CGContextSetBlendMode(context, CGBlendMode.Clear). While this works properly on the context of the UIView when I draw to the pdf context (as generated using UIGraphicsBeginPDFContextToData) the same code results in a line with the same color as set in CGContextSetStrokeColorWithColor. Does anybody know of an alternative way to achieve erasing in a pdf context?
For instance, when I run the code below a context from drawrect it results in a faint red line (alpha = 0.5) with a small gap running through the red line. However, if I supply a pdfcontext it becomes a faint redline with a hard red line running through it (as another thin red line with alpha 0.5 is superimposed)
let path = CGPathCreateMutable()
CGPathMoveToPoint(path, nil, 10, 10)
CGPathAddLineToPoint(path, nil, 10,100)
CGContextAddPath(context, path)
CGContextSetLineCap(context, CGLineCap.Round)
CGContextSetStrokeColorWithColor(context, UIColor.redColor().colorWithAlphaComponent(0.5).CGColor)
CGContextSetLineWidth(context, 10.0)
CGContextStrokePath(context)
CGPathMoveToPoint(path, nil, 10, 10)
CGPathAddLineToPoint(path, nil, 10,100)
CGContextAddPath(context, path)
CGContextSetBlendMode(context, CGBlendMode.Clear)
CGContextSetLineWidth(context, 2.0)
CGContextStrokePath(context)

Answer 1

I ended up solving my problem with a workaround. For the benefit of anyone else with this issue, here goes.
I draw subviews individually in the PDFContext. For each I check if it contains erasing. If this is the case I open a separate ImageContext and generate an image of the view as such.
UIGraphicsBeginImageContext(objectView.frame.size)
if let imageContext = UIGraphicsGetCurrentContext() {
objectView.drawObjectInContext(imageContext,rect: objectView.bounds)
self.applyEraser(imageContext, eraserShape: objectView.eraserLayer.eraseShape)
let image = UIGraphicsGetImageFromCurrentImageContext()
CGContextTranslateCTM(pdfContext, 0, objectView.bounds.height)
CGContextScaleCTM(pdfContext, 1.0, -1.0)
CGContextDrawImage(pdfContext, objectView.bounds, image.CGImage)
}
UIGraphicsEndImageContext()
Note that the image is upside compared to regular drawing in CGContext, which is why I invoke CGContextTranslate en CGContextScale.
The downside is that you get images of subviews in your PDF rather than perhaps simple text. However, if you do it for each view separately you can draw the views without erasing properly as text or whatever you want.