Truncated.swift

var isTruncating = false
// Make a range that encompases the entire text length.
let maxRange = NSRange(location: 0, length: Int.max)
// Use the layout manager to go through all of its line fragments within the range (entire text because of max range).
// More in-depth information is available within the NSLayoutManager docs.
layoutManager.enumerateLineFragments(forGlyphRange: maxRange) { _, _, _, glyphRange, stop in
  // Ask the layout manager to find the range of the truncation glyph (...) within this line fragment
  let truncatedRange = self.layoutManager.truncatedGlyphRange(inLineFragmentForGlyphAt: glyphRange.lowerBound)
  // If the truncatedRange has a valid location that means the layout manager has detected the truncation glyph.
  if truncatedRange.location != NSNotFound {
    isTruncating = true
    // NSLayoutManager uses a point to a boolean to know whether it should continue traversal.
    // Changing `stop` to point to a value of `true` halts the operation.
    stop.pointee = true 
  }
}