I am using core data to store favorites chosen by the user. I would like to know that if I send an app update, how can I keep the data of the favorites preserved after the app is updated by the user?
I have read that you could use versioning, but I'm not sure if this the correct method.
Any help will be appreciated! Thanks
If your app maintains the same bundle identifier and you don't copy over the core data store file, you keep it.
If you changed your Core Data model, then you do need to worry about versioning. Depending on changes you may need to write rules for migrating data in the old store to the new format. As you have probably experienced, if you change data structure and do not migrate (or wipe existing data), you crash.
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I am just about to update one application from me. This app uses Core Data for saving the data, which the user puts in.
Now I want to fix some bugs, which aren't associated with Core Data at all.
What do I have to do that the User gets his data after downloading the Update?
I don't think about Lightweight Migration, because I haven't changed anything.
Do I have to add a new Model Versioning File? - I don't know.
You don't have to to anything. If the model and the data is not updated as part of the update, and you are storing the user's data in the documents directory, then a new version of your app will just carry on using the existing data.
If you haven't changed your Core Data schema at all, then you don't have to do anything. It'll still read the old data files with no problem.
I already have an app in the app store. I want to do an upgrade. My local data store has changed, with an extra table, and with a few fields added in the existing table. I want to retain the data in the old tables. How would I go about doing that? Could someone point me to tutorials that handle that kind of change?
Assuming you're using SQLite: Use a new database with a different name for your update. On startup, check for the table with the old name, copy the data you want, and delete it when you're done.
CoreData has it's own update data which may or may not work for you. You should look into how to change the data model.
Check out Apple's docs on migrating a core data instance. They make it super easy for 90% of the cases. The basic idea, is you break you xdatamodel into versions, so it has a path for migration
Here's a tutorial that might help you Core Data Migration
I would like to update my app, but I have completely changed the data structure, so is the Core Data model entirely different. Now, the data in the app does not have to be preserved, but you can't just update the app with this new model as it will crash.
What is the best way to update my app?
You need to version the core data structure. Use this guide
http://developer.apple.com/library/mac/#documentation/cocoa/conceptual/CoreDataVersioning/Articles/Introduction.html
If you have a completely new data model you might look into having a new database persistent-store/db file and run a merge function if the app can find an old database.
Hoping to get some clear advice on this one.
I want to push updates to my app when it is live. I plan to do this by modifying the sqlite that ships with the app and then have the app download it. Easy.
I haven't worked out how actually get the app to see the new data though.. I can overwrite the sqlite in the documents directory, but the app has to be restarted for the new data to be picked up - no good. As a first step I don't mind if modifications to it are lost, but I am really looking for a way to keep any modifications to data, and add/remove entries based on the new sqlite. It will be the entire data-set rather than just the changes.
I am going down this path as the data is quite complex, but manageable through a desktop app based on same core-data model.
Is there a common way, or a way at all to achieve this?
Thanks.
There is no simple way to completely merge to two Core Data stores SQL or other wise.
Maintaining the integrity of the object graph requires that new data be inserted into the existing store via a context using the same model as that used to create the store. In other words, batch adding new data to the store is the same logical process as adding it one piece at a time from UI. You insert NSManagedObject instances, populate them, set their relationships and save them.
In theory, you could write great gobs of code to merge the old and new SQL databases into a new SQL store that Core Data could read. However, that is complex, unsupported and likely to break when Apple revs something in the future.
I would recommend having the app itself download the data piecemeal from the server and then insert the new data into the existing store. It's trivial to send data using something like JSON. Alternatively, you could download a new store, add it to the existing persistent store coordinator and then create clones the new objects in the old store. Then remove the downloaded store from the coordinator and delete the downloaded store file.
As far as I know, the Core Data store is stored in the application's documents directory.
If the user updates the application through App Store, all the data will be removed, right?
Can I save data to another place?
Thanks
Actually, the data should be fine. However, you will have to perform a migration if you changed the data model in the new version of your app.