Cocoa - 防止系统关闭
嘿伙计们， 我还有一个问题，在网上找不到答案。我希望你能帮助我。
我正在编写一个 Cocoa 应用程序，它在后台运行并为我执行多项任务。如果我退出应用程序，我会显示 NSAlert。这一切都很好。但我的问题来了。此警报是从 applicationShouldTerminate: 方法内部呈现的。因此，如果我注销，则会触发此方法并显示警报。但即使我返回 NSTerminateCancel，OSX 也会退出应用程序并注销，而不等待响应。
我如何强制操作系统停止从我的应用程序中注销/关闭，以便用户（我自己:-D）可以决定要做什么。 （这只是一个对话框，询问是否保存已完成的工作。）
我希望你能帮助我......
Sandro
Hey Guys,
I've another question I couldn't find an answer on the internet. I hope you can help me.
I'm writing an Cocoa Application which runs in background and does several tasks for me. If I quit the application, I show a NSAlert. That all works great. But here comes my problem. This Alert is presented from inside the applicationShouldTerminate: Method. So if I Logout, this method is triggered and the alert is shown. But OSX quits the application and logs out without waiting for a response even if I return NSTerminateCancel.
How can I force the OS to stop logging out/shutting down from within my application, so that the user (myself :-D) can decide what to do. (It just a dialog which asks if the done work shall be saved or not.)
I hope you can help me...
Sandro
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Mac OS X 基于 UNIX。当系统关闭时，会发送 SIGKILL 信号来终止所有进程。但在此之前，会发送 SIGTERM 信号，通知进程即将关闭。
我认为解决方案在于处理信号，即检测和阻止它们。关于这一点，您可以在 GNU 中找到指导C 库：信号处理：阻塞信号。
那里的示例可能是关于 BSD 的，但您可能知道 OS X 核心是从 BSD 派生的，因此 OS X 支持它。此外，Objective-C 也支持 C。
Mac OS X is based on UNIX. When a system shuts down, the SIGKILL signal is send that terminates all the processes. But before that, the SIGTERM signal is sent that informs the processes that a shutdown is going to take place.
I think the solution lies in handling of the signals, i.e. detecting and blocking them. Regarding this, you may find guidance in GNU C Library: Signal Handling: Blocking Signals.
The examples there maybe about BSD, but you may know that the OS X core is derived from BSD and therefore OS X supports it. Moreover, C is supported in Objective-C.