NSDocument 子类“close”方法被调用两次
我有一个基于文档的 Cocoa 应用程序，它将 NSDocument 子类为 MyDocument。每个MyDocument 管理一个单独的后台进程（作为NSTask）。我想确保 NSTask 在其相应的 MyDocument 关闭或整个应用程序退出时终止。
对于后者，我让文档观察 NSApplicationWillTerminateNotification。 对于前者，我重写 close 方法：（
-(void)close {
// Cleanup code here
[super close];
}
顺便说一句，我不能将清理代码放在 dealloc 方法，因为该项目是 GC 的。）
问题是这样的：如果我打开一个 MyDocument，进行未保存的更改，然后按 cmd-Q，close 方法被调用两次。从调试器来看，调用链是： [MyDocument close] 调用 [NSDocument close]，后者又调用 [NSWindowController _windowDidClose]，后者又调用 [MyDocument close] > 再次。 （调用之后，应用程序退出）。
这是预期的行为吗？如果是这样，是否有更好的方法来释放文档特定的资源？或者我应该让 close 安全地运行多次？
I have a document-based Cocoa application which subclasses NSDocument as MyDocument. Each MyDocument manages a separate background process (as an NSTask). I want to make sure that the NSTask is terminated when its corresponding MyDocument closes or when the whole application quits.
For the latter, I make the document observe NSApplicationWillTerminateNotification. For the former, I override the close method:
-(void)close {
// Cleanup code here
[super close];
}
(Incidentally, I can't put cleanup code in the dealloc method since the project is GC'd.)
The problem is this: If I open a MyDocument, make unsaved changes and then press cmd-Q, the close method is called twice. From the debugger, the call chain is:[MyDocument close] calls [NSDocument close], which calls [NSWindowController _windowDidClose], which calls [MyDocument close] again. (After that call, the application quits).
Is this expected behavior? If so, is there a better way to release document-specific resources? Or should I just make close safe to run multiple times?
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我相信我在 cocoadev 邮件列表上看到过一篇帖子，说这是目前框架的正常行为（但将来可能会改变）。您应该使您的
-close方法足够强大以处理多个调用，因为 AppKit 不保证它只会被调用一次。我不认为您需要关心
NSApplicationWillTerminateNotification，因为如果我理解正确的话，当您的应用程序也终止时，任务将自动终止。此外，如果您支持突然终止，您的应用程序可能会在没有通知的情况下被终止。I believe I've seen a post to the cocoadev mailing list saying that this is normal behaviour for the frameworks at the moment (but that it might change in future). You should make your
-closemethod robust enough to handle multiple calls since no guarantee is made by AppKit that it will be called only once.I don't believe you need care about
NSApplicationWillTerminateNotification, since if I understand correctly, tasks will automatically be terminated when your app is too. Furthermore, if you support sudden termination, your app can be killed without notice/notification anyway.