Fast Line Count

1

Anyone have a Swift (or ObjC) method to QUICKLY count the number of lines (\n) in an NSString?

The only method I’ve found so far is the equivalent of "split

2

Well, split IS pretty fast. Do you actually need to optimize this or are you trying to optimize the wrong part?

3

I need to update the line count whenever is could have possibly changed. So it needs to be rather quick, and keep a low footprint (a split duplicates the contents), and this string could be close to a meg . Right now I am trying to attach the recalcuation to everytime the user types [RETURN] or [BACKSPACE] (but also need to detect cuts and pastes)

The only other alternative is to just do it when ever the text changes, but that is quite often

4

came up with a way that seems to work

  1. if the user type [Return], [BS] or pastes then a flag is set
  2. in the textchange event if the flag is set it executes a RegEx
func textView(_ textView: NSTextView, shouldChangeTextIn affectedCharRange: NSRange, replacementString: String?) -> Bool {
    let s : String = String(replacementString!)
   if s.isEmpty || s=="\n" || s.count>1 { needRecount=true }
    return true
}

 func textDidChange(_ notification: Notification) {  // this fires is user TYPES into field
            if needRecount {
                let s       = self.string
                let regex   = try! NSRegularExpression(pattern:("(\\n)|(\\r)|(\\r\\n)"))
                let matchs  = regex.matches(in: s, range: NSRange(location: 0, length: s.count))//.map{(s as NSString).substring(with: $0.range)}
                print(matchs.count) <---- LINE COUNT IS HERE
                needRecount=false
            }
            self.needsDisplay=true
}
5

So it needs to be rather quick,

Can you do that in a thread that starts after the user types anything?

6

The above method is very fast, 30K lines in a split second…
BUT the answer is wrong… :frowning:
My text has 34783 lines, but the count returns as only 30442
mis counted by 4000 lines!

OR my linenumber display is wrong… guess I better figure out which it is :frowning:

7

So it could be faster…

650k lines counted in 0.74 seconds, that would create a bit of a lag in typing on a large file

8

WOW!!!
found a method that counted 1,564,850 lines in 0.14 seconds!!!

I think I’ll keep this one … (sorry guys, won’t work for Xojo)

func countLines(textView: NSTextView) -> Int {
    let layoutManager  = textView.layoutManager
    var numberOfLines  = 0
    var index          = 0
    var lineRange      = NSRange()
    let numberOfGlyphs = layoutManager!.numberOfGlyphs
    while index < numberOfGlyphs {
        numberOfLines += 1
        layoutManager!.lineFragmentRect(forGlyphAt: index, effectiveRange: &lineRange)
        index = NSMaxRange(lineRange);
    }
    print(numberOfLines)
    return numberOfLines
}
1 Like
9

Drag&drop?

10

Its tied to the TEXTCHANGE event… so drag&drop, paste, cut, type etc…

11

Ah, ok. You said earlier that you relied on key presses (see what I quoted from you), so I wondered…

12

Sorry… I solved that issue after I entered all that :slight_smile:

1 Like