Why does PhotoWatch use Apple App Groups instead of just Dropbox?

Question

Why does the PhotoWatch SwiftyDropbox sample take the design feature to use Apple App Groups instead of just a Dropbox folder? Is there a particular advantage in this design approach?

Greg-DB · Accepted Answer

I believe the app group was used as a convenient way to cache thumbnails for use across the iOS/watchOS versions of the app, after being retrieved from Dropbox, e.g., here:

https://github.com/dropbox/PhotoWatch/blob/48df3b99b47f4a883703f7a4cd9512eb2a5c0cb2/PhotoWatch/PhotoViewController.swift#L25

It's just an example app for demonstrating some Dropbox API calls though, so I wouldn't recommend taking too much general iOS app design guidance from it. Apple's resources are a better place for general iOS design information.