Do app updates overwrite the app's home directory?

I use the NSHomeDirectory() function to get the app's home folder, and write to开发者_JS百科 the Documents directory within that. I'm curious, though, what happens when the user downloads an update for the app from the App Store? Will it all be deleted? When I delete the app on the device, then reinstall it, it's wiped out. So, I'm curious to know what will happen with an update. I can't find this in the documentation at all.

Stuff inside ~/Documents/ and the user preferences are preserved during update.

See the iOS File System Programming Guide.