如何计算和显示iOS上的当前行号

Question

我创建了两个UITextView。一个用于行号，一个用于编辑。但是我似乎无法让前者显示行数。这是我到目前为止所写的内容，我确信我犯了一个错误，只是不确定在哪里。

var previousRect = CGRectZero        
var lineArray = ["1"]

func textViewDidChange(textView: UITextView) {

    let pos = editorView.endOfDocument
    let currentRect = editorView.caretRectForPosition(pos)
    if(currentRect.origin.y > previousRect.origin.y){
        //new line reached, write your code

        var i = 0
        i += 1
        lineArray.append("\(i)")
        let numberOfLinesString = "\(lineArray)"

        lineNumbering.text = "\(lineArray)\n"
    }            
    previousRect = currentRect
}