CoreData delete object in context

Question

Question:

Does deleting an NSManagedObject have to be done with in context.perform / context.performAndWait block ?
Or is it safe to delete the object outside the block ?

Code:

func delete(something: NSManagedObject, context: NSManagedObjectContext) {

    context.performAndWait { //Is context.perform / context.performAndWait required to delete an object ?

        context.delete(something)
    }
}

My thoughts:

Since this code was being called from different threads (both background / main ) it was better to use context.perform / context.performAndWait.
The context might have been created with a specific concurrent type (main / private queue).
The context's concurrent type would need to match that of the thread (main / background) in which the code was being executed.
The block would ensure it runs ok even if a thread with a different mismatched thread type is executing it.

score 0 · Accepted Answer · answered Apr 30 '18 at 06:44

0

As my personal experience, use performAndWait, because it will wait until operation done. Anyway, both method will run on it's own thread.(context's thread).

From Documentation:

perform(:) and performAndWait(:) ensure the block operations are executed on the queue specified for the context. The perform(:) method returns immediately and the context executes the block methods on its own thread. With the performAndWait(:) method, the context still executes the block methods on its own thread, but the method doesn’t return until the block is executed.

answered Apr 30 '18 at 06:44

Mani

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The question is not about whether to use `perform` or `performAndWait`. The question is should I use it at all or is it ok to delete without the block. I understand both would run on their respective threads, but the context might have been created with a specific concurrent type (main / private queue). My thought was context's concurrent type would need to match that of the thread (main / background). – user1046037 Apr 30 '18 at 06:47
1

I think you didn't understand. Ok let me explain. If you call `perform(:)` or `performAndWait(:)`, these method will place the execution block on the context's queue. Here no matter, where you calling from. If you call it from main/ background thread, that's not mean, the operation will place accordingly. It's a matter, context was created with what type. You no need to think about thread safe. It depends only on context's type. – Mani Apr 30 '18 at 06:51
I've seen your updated question. Third and fourth point is wrong understanding. – Mani Apr 30 '18 at 06:53

score 0 · Answer 2 · answered Apr 30 '18 at 08:17

In apple documentation it is being said about „...andWait” it works assyncronious. However „...andWait” should be used to catch the errors inside of perform block...

Moc.performBlock{ for jsonObject in jsonArray { let your = actions } do { try moc.save()

moc.performBlockAndWait { do { try moc.save() } catch { fatalError(„Failure to save context: (error)”) } } }...
Better to do it inside in case you have different values / unused values. In most cases ARC (memory management) should fix it.

You should also read here:

Core Data background context best practice

CoreData delete object in context

Question:

Code:

My thoughts:

2 Answers2