Mac App Disappears When Window Is Closed Then Another App Is Selected

Mac app disappears when window is closed then another app is selected

This behavior is known as Automatic Termination. I find it a misfeature, but Apple considers it a feature.

Your app may not have actually quit. It may just appear to have quit. "Launching" it again will just make it reappear in the Dock. It's also possible that some apps which look like they're still running have actually been terminated by the system. In theory, if you try to switch to them, they will be launched and told to restore their previous state to maintain the illusion that they were running all along. In practice, apps (even Apple's) rarely properly restore things to exactly how they were.

The process list in Activity Monitor is a true reflection for what is and is not actually running. Look there to determine if your app has really been terminated.

A developer is supposed to have to opt-in to Automatic Termination because it requires explicit coding of state restoration. However, Xcode's app project/target templates have it enabled by default. You can remove the NSSupportsAutomaticTermination key from your Info.plist to disable it.

Likewise, you'll presumably want to disable Sudden Termination, too, if you're not prepared to support it. You would remove the NSSupportsSuddenTermination key.

Macos app is getting closed when there're no windows open

Set NSSupportsAutomaticTermination to NO in your Info.plist.

Why does my MacOS app disappear on the dock when run/build on Xcode?

Found the issue. When I created another target, it was the same name as the MacOS file except a capitalized letter on it. Seems that it confused git and overwritten the MacOS file

Crash when closing window in a MacOS application?

The problem is the window is automatically released (and thus deallocated) upon closure. This, combined with the automatic reference counting, presumably creates a sort of double free error. To solve this problem without disabling ARC or disabling releaseWhenClosed, Window is made a global or instance variable. Doing so will prevent ARC from releasing the window after already having been released by being closed.

NSWindow *Window;
// ...
- (void)applicationDidFinishLaunching:(NSNotification *)Notification {
    Window = [[NSWindow alloc] initWithContentRect:(NSRect){.size = {800, 512}} styleMask:NSWindowStyleMaskTitled|NSWindowStyleMaskClosable|NSWindowStyleMaskMiniaturizable|NSWindowStyleMaskResizable backing:NSBackingStoreBuffered defer:YES];
    [Window center];
    [Window makeKeyAndOrderFront:Window];
    // Insert code here to initialize your application
}

OS X design decisions. Terminate the app on last window close?

Per Apple's Human Interface Guidelines (a guide for Mac developers):

In most cases, applications that are
not document-based should quit when
the main window is closed. For
Example, System Preferences quits if
the user closes the window. If an
application continues to perform some
function when the main window is
closed, however, it may be appropriate
to leave it running when the main
window is closed. For example, iTunes
continues to play when the user closes
the main window.

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