swift - 带有文本的文本字段中的退格键导致崩溃

Question

我有一个正在检查小写字母、大写字母、数字和特殊字符的文本字段。当我输入它们中的每一个时，它会做它应该做的事情。但是，如果我删除一个字符，它会崩溃。我很确定它与 0 有关，但我不确定该怎么做

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {

    let newText = range.length == 0 ? roomPasscode.text! + string : (roomPasscode.text! as NSString).stringByReplacingCharactersInRange(range, withString: string)

    let hasUppercaseCharacters = newText.hasUppercaseCharacters()
    let hasLowercaseCharacters = newText.hasLowercaseCharacters()
    let hasNumberCharacters = newText.hasNumberCharacters()
    let hasSpecialCharacters = newText.hasSpecialCharacters()
    let isTenCharactersLong = newText.characters.count == 10

    oneUpperMet.textColor = hasUppercaseCharacters ? .greenColor() : .redColor()
    oneLowerMet.textColor = hasLowercaseCharacters ? .greenColor() : .redColor()
    oneNumMet.textColor = hasNumberCharacters ? .greenColor() : .redColor()
    oneSpecialMet.textColor = hasSpecialCharacters ? .greenColor() : .redColor()
    tenCharMet.textColor = isTenCharactersLong ? .greenColor() : .redColor()



    if hasUppercaseCharacters && hasLowercaseCharacters && hasNumberCharacters && hasSpecialCharacters && isTenCharactersLong {
        clickableButton.tintColor = UIColor.greenColor()
    }

    return true
}

Answer 1

这个三元组的else参数:

let newText = range.length == 0 ? roomPasscode.text! + string : (roomPasscode.text! as NSString).stringByReplacingCharactersInRange(range, withString: string)

正在尝试删除一个不存在的字符。尝试像这样保留它以便快速修复:

let newText = range.length == 0 ? roomPasscode.text! + string : roomPasscode.text!