Random Thoughts

What’s new in Background Assets

Check out Meet Background Assets from WWDC 2022

Feature Recap

  • Designed to prevent waiting when launching your app, use a framework and App Extension to download out-of-band content via a CDN or managed server
    • It will download content that can be placed in your app’s sandbox for use by the app
  • Supported on macOS, iOS, and iPadOs
  • Can run periodically in the at install time before user runs the app, background, or when the app is not running
  • There are time limits on the run to optimize battery life
    • Consider memory mapping your data as you are also limited to amount of memory used by your app
    • The extension can be throttled if the app is not used very often
  • The Background Asset manager is prefixed with BA
  • User can turn off background app refresh turned off or is in low power mode – your extension will not run.
  • BADownloadManager is a singleton that can be used throughout your app. 
  • All downloaded assets are marked pursuable by default.  If you increase their size after download, they will be marked non-purgeable 

What’s New

  • Essential downloads – will be integrated into the system and will stop the user from loading the app.  They occur during app install.   These downloads have priority over normal background downloads.
  • Non-Essential downloads will be automatically launched after essential downloads are ready.  Note the UI changes that shows which part of the install download is App, App Install, and Essential assets.
  • If a user turns off In-App Content the you will not get essential downloads to download automatically.  You will need to code your application to handle download these assets different.
  • You can convert an essential download to a non-essential download, and the re-enque this download 
  • Also you need to setup your info.plist

Sample Implementation

  • First add your required info.plist keys
  • Create your App Extension
  • Make sure your app extensionMakes and app are both using the same team identifier
  • Make sure to use .withExclusiveControl for your download session 
  • Promoting from background to foreground does not restart the download, it just continues from where it was at a higher priority.
  • Always use move objects to move the finished download in to the app package
  • So far none of my apps have a need for these features.. but I do have a few game ideas which may need this in the future.  So definitely keeping this in my back pocket 

Debugging Guidance

  • Since the extension launches during the install or periodic system events.  You must use a tool called “xcrun backgroundassets-debug” in a terminal to be able to debug with a device paired with your Mac. The device must be in Developer Mode
    • You can now trigger events to see how the app or extension behaves.

Michael Rowe

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