CODEWITHSUNDEEP
iosswiftmultithreadingcore-data
Igor Kasuan
Igor Kasuan

Reputation: 842

Is it allowed to pass NSManagedObject through performBlock of the same NSManagedContext?

Can I set the relationship between objects in DIFFERENT perform blocks of the SAME NSManagedContext?

I created a private context and used (just example):

let pContext = persistentContainer.newBackgroundContext()
pContext.perform {
   let user = pContext.fetch(<fetch Request>).first
   pContext.performAndWait {
        let book = pContext.fetch(<another fetch request>).first
        book.name = "skjkjd"
        pContext.save()
        book.author = user
        pContext.save()
   }
}

May this code produce following error and in which cases?

Fatal Exception: NSInvalidArgumentException Illegal attempt to establish a relationship 'author' between objects in different contexts

Upvotes: 1

Views: 72

Answers (1)

Alexander
Alexander

Reputation: 1494

If I'm not mistaken but the AppDelegate persistentContainer.viewContext is a singleton. You shouldn't pass the MOC across threads the way you are trying to do.

Take a look at the apple documentation: https://developer.apple.com/documentation/coredata/using_core_data_in_the_background

TRY (not tested):

    let pContext = persistentContainer.newBackgroundContext()
    pContext.perform {
        let user = pContext.fetch(<fetch Request>).first
        let userObjcID = user.objectID
            pContext.performAndWait {
                 let book = pContext.fetch(<another fetch request>).first
                 book.name = "skjkjd"
                 // pContext.save()
                 book.author = pContext.object(with: userObjcID)
        pContext.save()
   }
}

Upvotes: 1

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