Swift-Force UITextview仅小写

lazy var myTextField: UITextField = {
    let textField = UITextField()
    textField.addTarget(self, action: #selector(forceLettersLowercased(_ :)), for: .editingChanged)
    return textField
}()

@objc func forceLettersLowercased(_ sender: UITextField) {
    sender.text = sender.text?.lowercased()
}

如何使用UITextView实现相同的功能?

lazy var myTextView: UITextView = {
    let textView = UITextView()
    return textView
}()

func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
      
    let textLowerCased = text.lowercased()

    textView.text = (textView.text as NSString).replacingCharacters(in: range, with: textLowerCased)

    let numberOfChars = textView.text.count
    
    return numberOfChars <= 200
}

我不断得到两个字母,比如当我键入字母“W”时,我得到一个小字母和一个大写字母,然后当我按backspace键时,我得到: [__NSCFString replaceCharactersInRange:withString:]: Range or index out of bounds