如何在swift 4中正确使用选择器

I have read many tutorials and even the official Apple documentation and must not understand what is wrong with this code.

我读过很多教程，甚至是苹果官方文档，我不应该理解这段代码有什么问题。

var dueDatePicker = UIDatePicker()

@IBOutlet weak var textField: UITextField!

override func viewDidLoad() {
    super.viewDidLoad()
    textField.inputView = dueDatePicker
    dueDatePicker.addTarget(self, action: #selector(datePickerValueChanged(_:)), for: UIControlEvents.valueChanged)
}

func datePickerValueChanged(_ sender: UIDatePicker){
    //Do Stuff
}

At runtime, I click on the textField and the UIDatePicker appears. The function that the selector points to is executed. As soon as I click a UI object outside of the UIDatePicker, the app crashes with this error:

在运行时，我单击textField，将出现UIDatePicker。选择器指向的函数被执行。当我点击UIDatePicker外的UI对象时，应用程序就会因为这个错误而崩溃:

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[YourApp.PromiseViewController dueDateChanged:]: unrecognized selector sent to instance 0x100b12ae0'

由于未被发现的异常“NSInvalidArgumentException”而终止应用程序，原因:PromiseViewController dueDateChanged:]::无法识别的选择器发送给实例0x100b12ae0'

What I don't understand is that the "selector" or pointer to the desired function is recognized initially. However, when I trigger another event from another UI Object this exception is thrown.

我不明白的是，“选择器”或指向所需函数的指针最初是被识别的。然而，当我从另一个UI对象触发另一个事件时，这个异常被抛出。

Why is this happening?

为什么会这样?

Shouldn't this exception be triggered when datePickerValueChanged() is called initially?

当datePickerValueChanged()最初被调用时，不应该触发这个异常吗?

2 个解决方案

#1

The error is telling you that an action with the selector dueDateChanged(_:) has been added as a target action.

错误是告诉您一个带有选择器dueDateChanged(_:)的操作被添加为目标操作。

More than one target action can be added to a control. Somewhere, maybe in your storyboard or xib, you have another action added to dueDatePicker.

可以将多个目标操作添加到控件中。在某个地方，可能在您的故事板或xib中，您有另一个动作添加到dueDatePicker。

#2

Just add @objc in front of your function

只需在函数前面添加@objc

@objc func datePickerValueChanged(_ sender: UIDatePicker){
    //Do Stuff
}

#1