how to add Line-numbers to uitextview?

Question

I want to add line-numbers to my uitextview. Do I have to write my own UI-Element? Or is there an other solition? Thanks for help!

Answer 1

There's nothing built-in for this. You'll have to do it yourself.

Answer 2

I had a similar requirement where I had to display the line number that the end-user's caret was at. This should probably help you (I did it from the view-controller):

- (NSUInteger)lineNumberFromCharacterIndex:(NSUInteger)aCharacterIndex
{

    NSLayoutManager* layoutManager = [scriptTextView layoutManager];

    NSUInteger numberOfLines = 0;

    NSUInteger glyphIndex = [layoutManager glyphIndexForCharacterAtIndex:aCharacterIndex] + 1;

    NSUInteger numberOfGlyphs = [layoutManager numberOfGlyphs];
    if (glyphIndex > numberOfGlyphs) {
        glyphIndex = numberOfGlyphs;
    }

    NSString* scriptText = [scriptTextView string];
    NSUInteger scriptTextLength = [scriptText length];

    if (scriptTextLength > 0 && aCharacterIndex >=  scriptTextLength && [scriptText characterAtIndex:scriptTextLength - 1] == '\n') {
        // Add 1 to the number of lines as the last bit of text is a carriage return and 
        // the caret will be on the whitespace in the text view after the last character
        numberOfLines++;
    }

    NSRange lineRange;

    for (NSUInteger currentGlyphIndex = 0; currentGlyphIndex < glyphIndex; numberOfLines++){

        [layoutManager lineFragmentRectForGlyphAtIndex:currentGlyphIndex
                                        effectiveRange:&lineRange];

        currentGlyphIndex = NSMaxRange(lineRange);
    }

    if (numberOfLines == 0) {
        numberOfLines = 1;
    }

    return numberOfLines;
}