Trap SIGINT in Cocoa macos application

Question

I am attempting to trap a SIGINT for a UI application made for MacOS. In the app delegate class, I see the following method:

func applicationWillTerminate(_          


        

Answer 1

Although I won't dare to compete with the great answers above, I think there is something important to say that may simplify the solution a lot.

I think your question mixes two very different levels of MacOS program life-cycle management.

True, you can run simple posix-style executables on Mac - but a Mac Cocoa app IS NOT a posix app with "attached UI". Mac application relies on a very verbose, complete, and feature-rich life-cycle mechanism that allows much more than anything posix process can -- from state preservation and restoration (when killed/re-launched) to being auto-launched in response to opening a file. Energy management, handling computer sleep, background and foreground transitions, attaching to the same app on close-by device, modes etc. etc.

Furthermore -- I can't see how one can ever expect a 'ctrl-C' from the keyboard to reach a Cocoa ("UI") application, as keyboard shortcuts are totally different in this context, and you can't run "UI" app from a terminal/shell synchronously.

Now the right wa to 'interrupt' a Cocoa app that is "stuck" or takes too long to perform something, is using the convention command-preiod key-combination, still widely implemented by many apps (Photoshop, video-editors, the Finder etc.) I'm sorry I could not locate this definition in Apple User Interface Guidelines - maybe it is no longer part of the standard. However, Ctrl-C certainly isn't!!!

you can implement Cmd-Period (⌘.) in your app (i.e. register for this high-level "interrupt" action, and handle it gracefully.

There is a good reason why NSApplication object wrapping the Cocoa App ignores SIGINT! it is completely out of context.