Data entered by user & app update

My app sends postcards via email. I开发者_如何转开发 have to do sent and drafts functionality. When users send postracd it's saved to "sent". All data will be stored via plist files.

How can I make my data (saved plist file) don't be deleted when app will be updated?

Have you considered using Core Data instead of simply storing it as a plist file? If so, there's something called Core Data Model Versioning and Data Migration, maybe you can read up on that? Here's the URL to that:

http://developer.apple.com/library/ios/#documentation/Cocoa/Conceptual/CoreDataVersioning/Articles/vmLightweight.html%23//apple_ref/doc/uid/TP40008426-SW1

Correct answer is here: http://developer.apple.com/library/ios/#documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/RuntimeEnvironment/RuntimeEnvironment.html#//apple_ref/doc/uid/TP40007072-CH2-SW7

Content of Documents and Library directories will be copied to the updated app place.