NSTimer 不调用私有函数作为选择器 [英] NSTimer does not invoke a private func as selector

问题描述

我正在研究一个要点:PasteboardWatcher.swift，其中我调用了一个像这样的 NSTimer 对象:

I am working on a gist: PasteboardWatcher.swift in which I invoked a NSTimer object like this:

func startPolling () {
        // setup and start of timer
        timer = NSTimer.scheduledTimerWithTimeInterval(2, target: self, selector: Selector("checkForChangesInPasteboard"), userInfo: nil, repeats: true)
}

checkForChangesInPasteboard 函数的定义是:

func checkForChangesInPasteboard() {
        // definition continues..
}

我不想将函数 checkForChangesInPasteboard 暴露给其他类，因此我想将其标记为私有，但出于某种原因，当我这样做时，它会引发以下异常:

I don't want to expose function checkForChangesInPasteboard to other classes, therefore I want to mark it as private but for some reason when I do so, it throws below exception:

-[PasteboardWatcher.PasteboardWatcher checkForChangesInPasteboard]: unrecognized selector sent to instance

如果我不将其标记为私有，它就可以完美运行.

If I don't mark it as private it works perfectly.

有什么办法可以让这个方法保持私有，对其他类隐藏它吗?

推荐答案

根据将 Swift 与 Cocoa 和 Objective-C 结合使用:

"标有 private 修饰符的声明不会出现在生成的标头中.除非用@IBAction、@IBOutlet 或 @objc 显式标记私有声明，否则它们不会暴露给 Objective-C."

" Declarations marked with the private modifier do not appear in the generated header. Private declarations are not exposed to Objective-C unless they are explicitly marked with @IBAction, @IBOutlet, or @objc as well."

摘自:Apple Inc.将 Swift 与 Cocoa 和 Objective-C 结合使用(Swift 2 预发行版)."电子书.https://itun.es/us/utTW7.l

Excerpt From: Apple Inc. "Using Swift with Cocoa and Objective-C (Swift 2 Prerelease)." iBooks. https://itun.es/us/utTW7.l

因此，您可以使用 @objc 标记您的函数以获得所需的行为.我刚刚在我使用公共可见性的一个应用程序中对此进行了测试，因为我认为 Objective-C 根本看不到私有声明，并且在标记为私有并用 @objc 装饰时它可以工作.

So, you can mark your function with @objc to get the desired behavior. I just tested this in one of my apps where I had used public visibility because I assumed that Objective-C couldn't see private declarations at all, and it works when marked as private and decorated with @objc.

我刚刚看到这个相关问题:使用目标选择器进行快速访问控制 - 基本上是一样的，但我认为你的措辞更笼统，所以严格来说不是重复.

I just saw this related question: Swift access control with target selectors — basically the same thing but I think yours is phrased in a more general way so not strictly a duplicate.

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