Will iOS Launch My App into the Background If It Was Force-Quit by the User

Will iOS launch my app into the background if it was force-quit by the user?

UPDATE2:

You can achieve this using the new PushKit framework, introduced in iOS 8. Though PushKit is used for VoIP. So your usage should be for VoIP related otherwise there is risk of app rejection. (See this answer).

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UDPDATE1:

The documentation has been clarified for iOS8. The documentation can be read here. Here is a relevant excerpt:

Use this method to process incoming remote notifications for your app.
Unlike the application:didReceiveRemoteNotification: method, which is
called only when your app is running in the foreground, the system
calls this method when your app is running in the foreground or
background. In addition, if you enabled the remote notifications
background mode, the system launches your app (or wakes it from the
suspended state) and puts it in the background state when a push
notification arrives. However, the system does not automatically
launch your app if the user has force-quit it. In that situation, the
user must relaunch your app or restart the device before the system
attempts to launch your app automatically again.

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Although this was not made clear by the WWDC video, a quick search on the developer forums turned this up:

https://devforums.apple.com/message/873265#873265 (login required)

Also keep in mind that if you kill your app from the app switcher
(i.e. swiping up to kill the app) then the OS will never relaunch the
app regardless of push notification or background fetch. In this case
the user has to manually relaunch the app once and then from that
point forward the background activities will be invoked. -pmarcos

That post was by an Apple employee so I think i can trust that this information is correct.

So it looks like when the app is killed from the app switcher (by swiping up), the app will never be launched, even for scheduled background fetches.

What will happen to my code when I force quit an iOS app?

UIApplicationDelegate method applicationWillTerminate(_:) will be called which gives you the opportunity to run code.

From the applicationWillTerminate(_:) - UIApplicationDelegate documentation:

This method lets your app know that it is about to be terminated and purged from memory entirely. You should use this method to perform any final clean-up tasks for your app, such as freeing shared resources, saving user data, and invalidating timers. Your implementation of this method has approximately five seconds to perform any tasks and return. If the method does not return before time expires, the system may kill the process altogether.

Your app is given an opportunity to save/cleanup before it is purged, and your method gets five seconds to run before the process is terminated by the operating system.

iOS: Does force quitting the app disables background upload using NSURLSession?

I can confirm now after a bunch of testing that background task will run ok if the app is just put into background. However, if user force quit the app manually, then iOS cancels all scheduled background tasks. So next time the app is launched I'm getting all the callbacks to the delegate with the error code of a canceled task.

Hope it helps someone looking into the same thing.

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