I made this simple UiViewRepresentable which displays line numbers and a super simple html syntax, (I am not going into detail here) but I wondered how I can make it so if I enter: “<” then the editor automatically enters: “>” and the cursors goes back one character. I am very new to UIKit and barely got this one working so help is nearly appreciated.

Here’s the editor code:

struct SourceEditor: UIViewRepresentable {
    @Binding var text: String
    @Binding var highlightText: String
    
    var theme: Theme
    
    func makeUIView(context: Context) -> SourceEditorClass {
        let textView = SourceEditorClass()
        textView.isEditable = true
        textView.delegate = context.coordinator
        textView.autocorrectionType = .no
        textView.autocapitalizationType = .none
        textView.keyboardType = .asciiCapable
        textView.font = UIFont.monospacedSystemFont(ofSize: 15, weight: .regular)
        textView.backgroundColor = UIColor(theme.backgroundColor)
        textView.textColor = UIColor(theme.textColor)
        textView.textContainer.lineBreakMode = .byWordWrapping
        
        // Add toolbar
        let toolbar = UIToolbar()
        toolbar.sizeToFit()
        
        let lessThanButton = UIBarButtonItem(title: "<", style: .plain, target: context.coordinator, action: #selector(context.coordinator.insertLessThan))
        let greaterThanButton = UIBarButtonItem(title: ">", style: .plain, target: context.coordinator, action: #selector(context.coordinator.insertGreaterThan))
        let flexibleSpace = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil)
        
        toolbar.items = [flexibleSpace, lessThanButton, greaterThanButton, flexibleSpace]
        
        textView.inputAccessoryView = toolbar
        
        return textView
    }
    
    func updateUIView(_ uiView: SourceEditorClass, context: Context) {
        context.coordinator.textDidChange = nil
        context.coordinator.selectionDidChange = nil
        
        if uiView.text != text {
            uiView.text = text
        }
        
        if uiView.theme != theme {
            uiView.backgroundColor = UIColor(theme.backgroundColor)
            uiView.textColor = UIColor(theme.textColor)
            uiView.theme = theme
        }
        
        context.coordinator.textDidChange = { newText in
            text = newText
        }
        context.coordinator.selectionDidChange = { text, selection in
            print(text.lineNumbersForRange(selection) ?? [])
            uiView.currentLines = text.lineNumbersForRange(selection) ?? []
            highlightText = ""
        }
        
        uiView.textStorage.addAttribute(.foregroundColor, value: UIColor(theme.textColor), range: NSRange(location: 0, length: uiView.text.count))
        uiView.textStorage.removeAttribute(.backgroundColor, range: NSRange(location: 0, length: uiView.text.count))
        uiView.textStorage.removeAttribute(.underlineStyle, range: NSRange(location: 0, length: uiView.text.count))
        
        if !highlightText.isEmpty {
            let ranges = findRegex(pattern: highlightText, text: uiView.text)
            for range in ranges {
                uiView.textStorage.addAttribute(.backgroundColor, value: UIColor.yellow.withAlphaComponent(0.8), range: range)
            }
        }
        
        for keyword in theme.keywords {
            let ranges = findRegex(pattern: keyword.regex, text: uiView.text)
            for range in ranges {
                if keyword.style == .foreground {
                    uiView.textStorage.addAttribute(.foregroundColor, value: UIColor(keyword.color), range: range)
                } else if keyword.style == .background {
                    uiView.textStorage.addAttribute(.backgroundColor, value: UIColor(keyword.color), range: range)
                } else if keyword.style == .underline {
                    uiView.textStorage.addAttribute(.underlineStyle, value: NSUnderlineStyle.single.rawValue, range: range)
                    uiView.textStorage.addAttribute(.underlineColor, value: UIColor(keyword.color), range: range)
                }
            }
        }
    }
    
    func makeCoordinator() -> Coordinator {
        return Coordinator(self)
    }

    class Coordinator: NSObject, UITextViewDelegate {
        
        var parent: SourceEditor
        var textDidChange: ((String) -> ())? = nil
        var selectionDidChange: ((_ text: String, _ selection: NSRange) -> ())? = nil
        
        init(_ parent: SourceEditor) {
            self.parent = parent
        }

        func textViewDidChange(_ textView: UITextView) {
            textDidChange?(textView.text)
        }

        func textViewDidChangeSelection(_ textView: UITextView) {
            selectionDidChange?(textView.text, textView.selectedRange)
            textView.setNeedsLayout()
        }
        
        @objc func insertLessThan() {
            insertText("<")
        }
        
        @objc func insertGreaterThan() {
            insertText(">")
        }
        
        private func insertText(_ text: String) {
            if let textView = UIResponder.currentFirstResponder as? UITextView {
                if let selectedRange = textView.selectedTextRange {
                    textView.replace(selectedRange, withText: text)
                }
            }
        }
    }
}

Please note that this code won’t run on its own because of the other requirements in the file. If you need it to fully test your code I can gladly give the full code including all files which are required to run it. Thanks in advance!