iOS 9's Space Saving "App Slicing" Feature Finally Ready
At long last, one of iOS 9 most useful but hidden feature is finally ready to save users some storage space on their iPhones and iPads. After wrestling with an unforeseen bug with the iCloud backend, Apple is now restoring the "App Slicing" feature, part of the larger App Thinning set, allowing developers to upload a single universal iOS or watchOS app to the App Store, confident in knowing that only the trimmed down variant for a specific device will be downloaded by the user.
Before iOS 9, developers would upload an iOS app that contained all the needed assets to work on any device supported device, regardless of form factor or hardware capability. This ensured that they are able to cover as many devices as possible without having to worry about creating specific versions for different devices and generations. The downside to this arrangement is that an iPhone user would be forced to download that universal version of the app, including the assets and code that are really only useful on an iPad, for example, or on a device with this or that GPU capability.
App Thinning puts those apps on a diet. In particular, app slicing ensures that only the resources absolutely required by a particular device is download by the user. It slices, hence the name, images according to the resolution and device category and similarly slices GPU resources based on hardware capability. The best part about this feature is that it is business as normal for app developers. They don't need to change their workflow and will still upload the same universal version of their apps to ITunes Connect. Everything is handled by the App Store automatically.
The feature was supposed to go out with iOS 9 last month but Apple discovered a bug that restored the wrong variant of an app for users migrating from an older device to a newer one. Now, that bug has seemingly been squashed and the feature is in full swing, which should give some peace of mind to those who opted to buy a 16gb iPhone.
SOURCE: Apple