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.
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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 have one app in the store with CoreData model, and i want change entirely the app (remove some garbage, organize, new CoreData model... etc).
So i thinking start over and create new project, what will happen when i try to upgrade the old app that is in the store to this new one? (i'm concerned about CoreData)
thanks a lot
If you change a core data model even slightly, you need to migrate data to the new model:
You can only open a Core Data store using the managed object model used to create it. Changing a model will therefore make it incompatible with (and so unable to open) the stores it previously created. If you change your model, you therefore need to change the data in existing stores to new version—changing the store format is known as migration.
That's from Apple's docs: http://developer.apple.com/library/mac/#documentation/cocoa/conceptual/CoreDataVersioning/Articles/Introduction.html
So if you want users to have their old data in your new version you're essentially going to have to replicate the old core data model in order to extract and migrate the data to your new model. For any release subsequent to that one, of course, you can get rid of the old model.
I have set up and app which has pre-populated data that copies the database to the project's store. Using the 'CoreDataBooks example' method:
Any way to pre populate core data?
For application upgrades, I want to add more data to the database but I don't want to change the existing database since new user data is stored there?
What's the best way to do this?
I'm thinking I would create a new versioned managed object model (I'm not sure if you can add a new MOM version if nothing in the schema actually changes), for new versions, read the currently running MOM version, migrate the MOM to the latest version and manually add the new records in the code that have not been added since the currently running MOM version.
It seems a bit tedious to manually add new records in the code. Does that sound right or is there a more elegant way to add this new data?
Thanks!
If you change the managed object model itself e.g. add a new entity or change an existing attribute, then you need to use migration to update the existing persistent store. See the Core Data docs for details on migration.
If you just want to add new data, then you don't have any choice but to do so "manually."
Remember, Core Data is an object graph management system, not a database. An object "graph" is a "web" of interrelated objects so the only way to add data to the graph is to create new objects and set their relationships. It's not inefficient, it just the way it works.
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.
I have an application in iTunes app store using core data. Currently I'm developing a new version that has a new core data model. I do not want to migrate the data when updating. I just want to remove the old one and in with the new.
Whats the best way to handle this? My current (temporary?) solution is to change the path of the sqlite file which leaves the old database in the app.
Is there a migration option to remove the store if it can not be migrated, or some other solution?
I would probably check for the existence of the original database using NSFileManager and delete/remove it if found. The best place to do this is probably when you create the persistent store that Core Data uses.