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I'm new to Stack Overflow and have been programming for only a year, so still a newbie with this stuff (i.e., please bear with me!). I'm upgrading an old app created in xcode 3 that uses an sqlite database to store user-generated data. The upgraded app needs to work with iCloud, so I've decided to switch to Core Data (because sqlite on its own can't be synced with iCloud). I have no problem implementing the Core Data structures but my problem is in how to allow users to retain their existing data.

I have already looked at topics along these lines: How to import a pre-existing sqlite file into Core Data? and Need To Populate Core Data From SQLite Database, and while I can create a utility app to import existing data, this is of no use because there is no existing data with the initial app bundle, the data is stored by the user.

I'd really appreciate any help I can get on this, have totally tied myself in a big knot over it! Maybe I'm better off avoiding core data altogether and finding another solution to save the sqlite data in iCloud?

Thanks in advance!

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Nicole S
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1 Answers1

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You can use core data. Create your core data model and stack, and your migration process consists of querying chucks of data from your sqlite database to insert them into the core data database.

Let's say that you have three tables in your sqlite. Person, Vehicle, and Property. You will create the equivalent entities in your core data mode, then you will have to query information from these tables to insert them into core data. You need to get familiar on how to insert data into a core data database, and how to use it on a multithreading environment (to avoid locking the application during the migration process).

Here's a few things to keep in mind:

  • Try to save in chunks. Do not load everything into memory, but also you must avoid making numerous save calls into your NSManagedObjectContext instance. Every save call into the context is IO. Balance IO and memory depending on your data usage.
  • Index the properties you have on your existing entities that can be indexed. This will help you build relationships (if any)
  • Ask the system for time before starting the migration. Use UIApplication's beginBackgroundTaskWithExpirationHandler: in order to be sure to have enough time from the system to continue the migration (in case the user sends the application to the background).
  • Do not bother cleaning the sqlite database. Delete the database file when you are done with it.

These are some of the things I can advice to you for now. If i think of more, I will edit this post. Best of luck.

J2theC
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