NSTimer不会调用私有函数作为选择器

问题描述

我正在研究要点：，其中我调用了NSTimer像这样的对象：

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)
}

其中 checkForChangesInPasteboard 函数的定义是：

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

我不想将函数 checkForChangesInPasteboard 公开给其他类，因此我想将其标记为私有，但是出于某种原因，它会在下面抛出例外：

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

的tor如果我不将其标记为私有，则效果很好。

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

有什么方法可以将这种方法保留为私有的，并在其他类中隐藏？

推荐答案

根据在Swift中使用Cocoa和Objective-C ：

声明标有private修饰符的标记不会出现在生成的标题中。除非私有声明也被@ IBAction，@ IBOutlet或@objc明确标记，否则它们不会暴露于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."

摘录自：Apple Inc.将Swift与Cocoa和Objective-C结合使用（Swift 2预发行版）。 iBooks。

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 标记函数以获得所需的行为。我只是在其中一个使用了公开可见性的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 。

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.

我刚刚看到了以下相关问题：-基本上是同一件事，但我认为您的表达方式较为笼统所以不是严格重复。

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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