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PO
 

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    <p>First, what is the crash?</p> <p>Second, Core Data generally is a single threaded API. There are things you can do in multiple threads but creating a <code>NSMappingModel</code> is most likely not one of them. Why <em>must</em> you create the mapping model dynamically? If the MOMs are a known quantity then the mapping can be a known quantity as well.</p> <h2>update</h2> <p>First, the threading issue. Core Data is meant to be single threaded. However, the <code>NSManagedObjectContext</code> knows how to lock the <code>NSPersistentStoreCoordinator</code> correctly therefore you can have one <code>NSManagedObjectContext</code> per thread because they know how to lock correctly. However this is not the case when you are working with and creating a mapping model. </p> <p>However, the error you provided is not a Core Data error <em>per se</em>. That error indicates that somewhere in your code you are trying to stick a nil into a set. Without seeing the code that is generating the mapping model though it is difficult to guess as to exactly where.</p> <p>Have you put a breakpoint at objc_throw_exception and see what line in your code is causing this crash? If it is in something non-obvious then I would suggest there is some point in your building of the mapping model that is giving Core Data an unexpected nil.</p> <p>One thing you can try is locking the <code>NSPersistentStore</code> and/or the <code>NSManagedObjectContext</code> yourself to see if that resolves the crash. However I suspect when you do that you are going to again deal with performance issues.</p>
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    1. POCrashes in Core Data's Inferred Mapping Model Creation (Lightweight Migration). Threading Issue?
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    1. USMarcus S. Zarra
    1. USMarcus S. Zarra
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    1. COI have pasted the crash here: http://pastie.org/private/jjeuc3my4kjjjiwcpqgwnw I must create the mapping model dynamically because the MOMs are only known dynamically. But what is fundamentally wrong with creating a mapping model in another thread? There possibly cannot be anything in this that is messing up my data store in any way whatsoever. Maybe I need to somehow find a way to create the mapping model on the main thread? Hmm, that would make it tricky for me to avoid the beachball.
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    2. COActually, the above crash is not the only type of crash that occurs. I have seen 2 other types. Just like whether a crash occurs in the first place is unpredictable, which of these 3 crashes occurs is also unpredictable. I was finally able to repreoduce one of those 2 other types of crashes: http://pastie.org/private/wk33phudn48griryzdqzua
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