My iOS Application has been in review, but was rejected regarding the iOS Data Storage Guidelines. In the end, it was rejected because my Core Data database (sqlite) was located in the /Documents folder. I’m was aware, that this folder should only be used, it the data could not be recreated by my application. The reason why I chose to put it there anyway was, that one of the entities in my database contains an attribute telling if the given news has been read. This information cannot be recreated. Is this not enough to put the database in the /Documents folder?
Another thing is, that the current version of my application does not use this value to visualize if the news item has been read or not. So, should I tell the review-team about this attribute and argument why I think it should be placed in the document-folder — or should I just move it to the /Library/Cache/?
The app review team wants you to split your data apart. Store the re-creatable parts in the Cache folder and the stuff that can’t be re-created in the Documents folder. It’s okay if there’s a little bit of stuff in Documents that could theoretically be re-created—nobody will even notice a title or datestamp—but long text documents, video, audio, or images should be kept in the Cache folder if they can be downloaded again later.
There are a couple different ways you could do this:
Store the downloaded content in the Cache folder and only put the content’s filename in your Core Data database (or calculate the filename from something else, like the SHA-1 hash of the URL it was downloaded from). Make sure your code will re-download any content that’s not in the cache.
Use two Core Data stores with a single store coordinator. Note that you can’t split an entity’s attributes across two stores, so you may have to break some of your entities in half. Nor can you create a relationship from an object in one store to an object in another, so you’ll have to store the object ID URI instead. See “Cross-Store Relationships” in the “Relationships and Fetched Properties” section of the Core Data Programming Guide for more details.
Whatever you do, keep in mind that iOS may purge your Cache folder at any time. Be prepared for files in your Cache folder to have disappeared; if that happens, you should re-download the files as the user requests them.