Do NSUserDefaults persist through an Update to an app in the Appstore?
I beleive the answer is YES, it will persist. This also fully documented under the Application Directory chapter in the Apple iPhone OS Programming Guide.
They are usually not reset unless the user deletes the app. For basic data, NSUserDefaults is the best way to save data such as preferences, dates, strings etc. If you are looking to save images and files, the file system is a better bet.
- Direct answer to the posted question: YES.
- Your problem: Your app gets crashed due to logic issues. Suppose you store an object in defaults and the app checks it's value on launch (or elsewhere). In you update you could change the way it is checked or used, e.g. you expect a value, but the object is nil, or vice versa. This may cause a SIGABRT or EXC_BAD_ACCESS.