MagicalRecord: Setting up core data stack on a background thread

Question

One of the things Marcus Zarra recommends in his Core Data book when talking about setting up an app's core data stack is to put calls to addPersistentStoreWithType:configuration:URL:options:error: on a background thread, because it can take an indeterminate amount of time (e.g., to run migrations). Is there a simple way to tell MagicalRecord to do that? It looks like all of its setupCoreDataStack... methods perform everything on the calling (presumably main) thread.

I don't think it makes sense to just move the top-level setup calls onto a background thread, because it wouldn't be safe to start using MR from the main thread until at least the contexts had been created, right? Do I need to implement my own setupCoreDataStackWithAsyncMigration or somesuch thing?

Answer 1

There is the wwdc2012 example code for setting up iCloud on a background thread (Shared Core Data sample). You could refractor the CoreDataController to use MagicalRecord (and ignore anything iCloud). IIRC the locking mechanism, to stop other threads from accessing the store while the setup is in progress, is already present.

Before you go down that route measure the time needed to startup on the device. If the startup is fast enough for your needs then you might want to stick with the setup on a main thread.

Migrations can take some time but migration won't occur on every app launch. Migration time depends on data volume and complexity of changes between model versions. So again it is a judgment call to invest time to move the migration to a background thread or to keep the user waiting.