是否可以从 Swift 中 UITextView 元素的光标位置获取索引 (String.Index) 值？

Question

我希望从 UITextView 元素的用户光标位置提取索引值 ( String.Index )。 我正在使用selectedTextRange方法来获取 UITextRange 值。 如何使用它来检索索引值？

Answer 1

您可以获得从文档开头到所选范围开头的选定范围偏移量，并使用该偏移量来获取字符串索引，如下所示：

extension UITextView {
    var cursorOffset: Int? {
        guard let range = selectedTextRange else { return nil }
        return offset(from: beginningOfDocument, to: range.start)
    }
    var cursorIndex: String.Index? {
        guard let location = cursorOffset else { return nil }
        return Range(.init(location: location, length: 0), in: text)?.lowerBound
    }
    var cursorDistance: Int? {
        guard let cursorIndex = cursorIndex else { return nil }
        return text.distance(from: text.startIndex, to: cursorIndex)
    }
}

---

class ViewController: UIViewController, UITextViewDelegate {
    @IBOutlet weak var textView: UITextView!
    override func viewDidLoad() {
        super.viewDidLoad()
        textView.delegate = self
    }
    func textViewDidChangeSelection(_ textView: UITextView) {
        print("Cursor UTF16 Offset:",textView.cursorOffset ?? "")
        print("Cursor Index:", textView.cursorIndex ?? "")
        print("Cursor distance:", textView.cursorDistance ?? "")
    }
}