ios 可选类型字符串的值？没有打开
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Value of optional type String? not unwrapped
提问by Insane
I am just not able to unwrap elseblock. xCode gives me options to "Fix it with ! and ??", which sadly does not fix the issue either.
I get this error in xCode:
Value of optional type 'String?' not unwrapped; did you mean to use ! or ??
我只是无法解开else块。xCode 为我提供了“使用 ! 和 ?? 修复它”的选项，但遗憾的是，这也不能解决问题。我在 xCode 中收到此错误：可选类型“字符串？”的值 未解开；你是想用吗！或者 ？？
@IBAction func buttonTapped(theButton: UIButton) {
if answerField.text == "0" {
answerField.text = theButton.titleLabel?.text
} else {
answerField.text = answerField.text + theButton.titleLabel?.text
}
回答by ZYiOS
Because theButton.titleLabel?.text it not unwrapped.
因为 Button.titleLabel?.text 它没有解开。
You can use
您可以使用
answerField.text = answerField.text + (theButton.titleLabel?.text ?? "")
or
或者
if answerField.text == "0" {
answerField.text = theButton.titleLabel?.text
} else {
if let txt = theButton.titleLabel?.text {
answerField.text = answerField.text + txt
} else {
answerField.text = answerField.text
}
}
