Apple AppStore update process: how it affects the existing files

Question

from what I understand an Apple app update would be installing a new standalone application instead of applying a patch to the existing one.

Does anyone know more details about this process? This applies to all the directories for the user? Any folders like Private Documents will be left untouched by the update. How about the other folders like Documents, etc.. I am hoping to find a document describing the behaviour, but could not find one so far on the web.

By update I mean: let's say the user has version 1.2 ... and then pulls data from the application server when available. And then 1.3 comes online to the App Store.. the user updates to 1.3.

Answer 1

As explained here: iOS App Programming Guide, all you need to know about updates is that:

Files Saved During App Updates

When a user downloads an app update, iTunes installs the update in a new app directory. It then moves the user’s data files from the old installation over to the new app directory before deleting the old installation. Files in the following directories are guaranteed to be preserved during the update process:

• Application_Home/Documents
• Application_Home/Library

Although files in other user directories may also be moved over, you should not rely on them being present after an update.