saving a file outside of my application bundel in iphone

i want to save a file 开发者_如何学Pythonoutside of my application bundle as a backup of database so that when user reinstall my app or my app crashes he can backup his data from that location.

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Apple already does this, with iTunes.

What you are asking is technically against apple's policy, unless you store it off site, on a server (which you could easily do)

If you have a lot of applications, I'm not aware of the policy, but perhaps you could make an app to back up your other app's data.