swift - 在将其保存到属性时追加字符串并在调用它时将其删除

Question

我喜欢在eventTextField.text中添加"abc"，保存到下面的属性eventName

eventInformation.setValue(eventTextField.text, forKey: "eventName")

我试过了

let abcString = "abc"
eventInformation.setValue(eventTextField.text?.append(abcString), forKey: "eventName")

但我的应用因以下错误而崩溃

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Unacceptable type of value for attribute: property = "eventName"; desired type = NSString; given type = _SwiftValue; value = ().'

Answer 1

错误发生是因为append正在改变但没有返回任何东西，
那是 _SwiftValue；值 = () (无效)

您需要一个额外的步骤:

let abcString = "abc"
eventTextField.text?.append(abcString)
eventInformation.setValue(eventTextField.text, forKey: "eventName")