Let’s start by simplifying the problem. Your phone (and your Wii controller, I believe) have three accelerometers oriented at right angles to one another. We’re going to study the behavior of just one accelerometer. Once you understand the behavior of one, extending it to three is easy.
I thought I’d leave an open question:
1) Do you know of an app whose future is put in jeopardy by sandboxing? (Ideally: an app that you wrote)
2) Is it so bad that there’s a real risk that the app will be frozen in its pre-sandboxed state?
The save fails because the underlying SQLite library created temporary files on behalf of Core Data. You may have seen a file like this. Usually this file has the suffix “-journal”. When you activate sandboxing your application is only are allowed to read and write to the store file itself and not to the “-journal” file. This explains why the save of the context fails.
Sandboxing is incompatible with the default way of saving Core Data files. Developers filed bugs about this as soon as sandboxing was announced last June, but there has been no change. The workaround is to turn off database journaling, which puts your data at risk in the event of a crash or power failure.
