I have this SwiftUI UiViewRepresentable which I want to use to make a simple TextEditor with line numbers. However the line numbers don’t get drawn. I a very new to UIKit and this is most I was able to do. Can anyone please help me to draw the numbers. I also don’t need the last line number when the last line is empty. aka. n. Thanks in advance.

//
//  Editor.swift
//  Code+
//
//  Created by Karl Ehrlich on 24.04.24.
//

import SwiftUI

class TextViewContainer: UITextView {
    
    init(text: String) {
        super.init(frame: .zero, textContainer: nil)
        self.text = text
        setupTextView()
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    private func setupTextView() {
        backgroundColor = .white // Set background color to white
        font = UIFont.monospacedSystemFont(ofSize: 15, weight: .regular) // Set font to monospaced system font
        isEditable = true // Allow text editing
        isSelectable = true // Allow text selection
        dataDetectorTypes = .all // Enable data detection
    }

    override func layoutSubviews() {
        super.layoutSubviews()
        
        var currentLine = 1
        
        layoutManager.enumerateLineFragments(forGlyphRange: NSRange(location: 0, length: textStorage.length)) { (rect, usedRect, textContainer, glyphRange, stop) in
            print("Line: (currentLine)")
            
            let attributes: [NSAttributedString.Key: Any] = [
                .font: UIFont.monospacedSystemFont(ofSize: 12, weight: .light),
                .foregroundColor : UIColor.gray,
            ]
            
            let attributedString = NSAttributedString(string: "(currentLine)", attributes: attributes)
            
            attributedString.draw(in: rect)
            
            currentLine += 1
        }
    }
}

struct Editor: UIViewRepresentable {
    @Binding var text: String

    func makeUIView(context: Context) -> TextViewContainer {
        let textView = TextViewContainer(text: text)
        textView.contentInset = UIEdgeInsets(top: 0, left: 40, bottom: 0, right: 0) // Set content inset to indent by 40 pixels on the left
        return textView
    }

    func updateUIView(_ uiView: TextViewContainer, context: Context) {
        uiView.text = text
    }
}

I tried to use a separate UIView but it also didn’t work. Here is my usage.

import SwiftUI

struct ContentView: View {
    
    @State private var text = """
let a = 0

Hello, World!
This is my syntax highlighting editor using „TextKit 2“
"""
    
    var body: some View {
        Editor(text: $text)
    }
}

#Preview {
    ContentView()
}