从textView中的字符索引中获取单词(iOS)

let text = textView.text
let selectedRange = textView.selectedRange

if selectedRange.length == 0 {
    return
}

let start = selectedRange.location

let backwardCharacterSet = CharacterSet(charactersIn: " .,;?!")

var wordStart = text.rangeOfCharacter(from: backwardCharacterSet, options: .backwards, range: NSRange(location: 0, length: start))
if wordStart == nil {
    wordStart = NSRange(location: 0, length: start)
} else {
    wordStart = NSRange(location: wordStart!.upperBound, length: start - wordStart!.upperBound)
}

let forwardCharacterSet = CharacterSet(charactersIn: " .,;?!")

let wordEnd = text.rangeOfCharacter(from: forwardCharacterSet, options: .literal, range: NSRange(location: start, length: text.count - start))

let wordRange = NSRange(location: wordStart.location, length: wordEnd!.upperBound - wordStart.location)

let word = (text as NSString).substring(with: wordRange)

print("单词：\(word)")