Core Data: Error when deleting/adding objects

Question

Sometimes my app crashes when I want to update my Core Data file by downloading and parsing a json file. I get the following error:

CoreData: error: Serio

Answer 1

You shouldn't be accessing your managed object context on serialQueue. Take a look at the Concurrency section of the NSManagedObjectContext documentation.

If in your code your context is using NSPrivateQueueConcurrencyType or NSMainQueueConcurrencyType concurrency type, you can use one of the block-based methods to ensure you're on the right queue:

//asyncrhonous
[self.managedObjectContext performBlock:^{
    //do stuff with the context
}];

//syncrhonous
[self.managedObjectContext performBlockAndWait:^{
    //do stuff with the context
}];