CODEWITHSUNDEEP
objective-ccore-data
Slee
Slee

Reputation: 28248

Does accessing a property on an NSManagedObject from a background thread make the context cross that thread?

I need to use a property on my NSManagedObjectContext as a parameter in a method that runs in the background. After this method is called I then have problems from that point forward with that context even though all I did was get a property value.

Upvotes: 2

Views: 1041

Answers (1)

Michał Ciuba
Michał Ciuba

Reputation: 7944

From the docs:

Any time you manipulate or access managed objects, you use the associated managed object context. Core Data does not present a situation where reads are “safe” but changes are “dangerous”—every operation is “dangerous” because every operation has cache coherency effects and can trigger faulting.

I've been working with Core Data in multi-threaded apps for some time (also in pre-iOS 5 era, without parent contexts etc.). I suspect it does some threading voodoo (locks and stuff) under the hood. If you want to be 100% safe, in a background thread you can't call any method on a NSManagedObject if its NSManagedObjectContext has not been created on the same thread. Otherwise, Undefined Behavior may happen (I got some deadlocks, for example).

Upvotes: 3

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