CODEWITHSUNDEEP
iosswiftcore-data
Christopher Francisco
Christopher Francisco

Reputation: 16278

Core Data merge error when deleting object

I have an entity A that has many B. B belongs to A.

When I load data from network, since I've read performing upsert operations with core data is either imposible or that's not the way it's supposed to be handled, I went for the delete/insert way.

When I try to delete all A, I get an Code=133020 NSMergeConflict. It makes sense because: 1) Where would those B entities that belongs to A end up, and 2) I don't want to delete B as in a delete cascade. I literally just want to update A.

That being said, it is clear delete/update is not the way to go (or at least not the way I'm doing it). So what's the proper way to handle this?

Upvotes: 0

Views: 84

Answers (1)

Mundi
Mundi

Reputation: 80271

Right, delete update would require you to keep track of the to-many relationship objects as well and re-assign them to the new object. Because you also have to re-assign all other attributes, this seems to be much more work than just checking if the object already exists.

I am sure your network service has some unique attribute, such as an idNumber. You can use that to first do a lookup. 

let filteredAObjects = allAObjects.filter { $0.idNumber == idNumberFromWebService }
let objectToUpdate = filteredAObjects.count == 0 ? 
  NSEntityDescription.insertNewObjectForEntityWithName("A",
                      inManagedObjectContext: moc) as! A :
  filteredAObjects.first

Upvotes: 2

Related Questions