Question

I just read on this answer(answer has since been removed) and I’m sure I’ve seen apps crash after hanging so what I read made sense.

If you block the main thread for too long the OS will kill your app.

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However I wrote a few tests and found that none of them caused the app to crash after waiting approx 2-5 mins on each. Breakpoints confirmed that I’m running on the main thread.

• Can someone confirm or disprove what I read please or have I just picked a lot of options which are non-blocking?

• If I have picked non blocking options, can somebody explain why these are non-blocking?

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while (true) { /*Nothing*/ }

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while (true) { NSLog(@"nothing"); }

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for(;;);

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sleep(100000000);

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while(true) { sleep(1); }

Answer 1

iOS will only kill your app if it spends too long in some of the UIApplicationDelegate methods like application:didFinishLaunchingWithOptions: or applicationDidEnterBackground:. You usually have 5 seconds to return, although this is not enforced for debug versions of your application.

Blocking the main thread outside of these methods will not cause your application to be terminated.