Measuring the height of lines in UITextView - ios

Question

I am trying to measure the height of lines to place an overlay over specific text in a UITextView. Specifically what I mean by lines is text delimitated with \n. So one line can actually span multiple lines and that is what I am trying to measure. I have tried a few different approaches, however, I can't seem to calculate the height correctly. Another weakness with my current approaches is it has to be all calculated on the main synchronous thread which is less than ideal because I have a lot calculations to do.
EXAMPLE UI APPROACH
measurement.font = UIFont(name: "Menlo", size: 16)
measurement.frame = CGRect(x: 0, y: 0, width: 10000, height: 50)
func heightForString(line: String) -> CGFloat {
var height : CGFloat = 0
measurement.frame = CGRect(x: 0, y: 0, width: self.view.frame.width, height: 10000)
measurement.sizeToFit()
height = measurement.frame.height
print(height, lineHeight)
measurement.frame = CGRect(x: 0, y: 0, width: 10000, height: 50)
return height
}
// Comparing the returned height to measurement.font?.lineHeight and padding shows the results make little sense... :(
EXAMPLE PRINT
Should be 1 line
30.0 18.625
Should be 3 lines
43.6666666666667 18.625

Answer 1

func heightForString(line: String) -> CGFloat {
let textView = UITextView()
let maxwidth = UIScreen.main.bounds.width
textView.frame = CGRect(x:0,y: 0,width: maxwidth,height: CGFloat(MAXFLOAT))
textView.textContainerInset = UIEdgeInsets.zero
textView.textContainer.lineFragmentPadding = 0
textView.font = UIFont(name: "Menlo", size: 16)
textView.text = line
textView.isScrollEnabled = false
textView.sizeToFit()
return textView.frame.size.height
}