I want to upload a new beta version of my iOS application for beta testers group. Users save their data in the Documents folder. What do I need to do in order for users to upgrade their application without losing their data?
The Documents directory is not overwritten when you update an app so as long as your data is compatible between versions, you shouldn't have to do anything special.
Alternatively, for developers, Xcode's Organizer allows you to extract the contents of an apps Documents directory easily.
Downgrading iTunes to 7.7 seems solved the problem on Windows
来源：https://stackoverflow.com/questions/941479/preventing-erasure-of-user-data-while-upgrading-ios-application-via-itunes