Crash saving background context about coredatastack HOT 9 CLOSED

Can you tell us which version of this library you're using?

Because we're using an unowned reference to self in the saveContext method, and that method executes asynchronously, it's possible for the NSManagedObjectContext instance to be deallocated by ARC before the async save block executes. If you're doing background work on another thread/queue that calls saveContext and finishes its work before that block is done, this could result.

While we could use weak and prevent the crash, it may make the code in saveContext a no-op, which is probably not what you would expect.

We'll look at making the memory semantics of this more clear, but the better fix is probably to use saveContextAndWait for background operations in your code instead.

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It might be more in keeping with the intent of a save call to drop both unowned and weak and instead hold a strong reference to the object till the save completes. I think this would take only a two-word change: remove the [unowned self] in saveContext from SaveHelpers.swift:51.

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@jeremy-w I like this idea. 👍 I'll let @lyricsboy take a look today and see if we can put a unit test together to cover this case before proceeding.

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Can I help with it?

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@bitomule: Sure, the unowned -> strong switch outlined above will hopefully fix it. If you could apply that and verify that it stops your app from crashing, that would be awesome. :D

BTW, did the crash happen reliably for you, or was it only sometimes crashing?

I think @rcedwards was hoping to put a test over it, but that will be hard without introducing something like "build test-only project, run the executable from the test, wait for it to exit, fail if it didn't exit cleanly", since a failing test within the test process will kill the test process itself and prevent running other tests. :)

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@jeremy-w that could fix it but my issue only happened once after a lot's of saves so not easy way to test it.

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Addressed in https://github.com/bignerdranch/CoreDataStack/releases/tag/v1.0.2

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Thanks, will report if it occurs again. Btw, today we released our iOS app with a powerful core data stack 👍

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@bitomule fantastic news 🎉 We're happy our stack was able to help with your project.

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