Storage Locations
iCould Drive
Accessible across all devices
Cached locally
Automatically uploaded to iCloud
Requires file coordination
Documents Directory
User-visible content
Accessible in Files app
Support "Open in Place"
Support "File Sharing Enabled"
Storage Settings management
Application Support Directory
Required files
Can be hierarchical
Persistent
Included in iCloud and iTunes Backups
Reported in "Documents & Data"
Caches Directory
Purgeable or transient content
Good for downloadable storage
Not included in backups
Reclaimed by OS if needed
Temporary Directory
Transient files
Remove when done
Not included in backups
Storing Your App’s Data Efficiently
To ensure that backups are as efficient as possible, store your app’s data according to the following guidelines:
Only documents and other data that is user-generated, or that cannot otherwise be recreated by your application, should be stored in the <Application_Home>/Documents directory and will be automatically backed up by iCloud.
Data that can be downloaded again or regenerated should be stored in the <Application_Home>/Library/Caches directory. Examples of files you should put in the Caches directory include database cache files and downloadable content, such as that used by magazine, newspaper, and map applications.
Data that is used only temporarily should be stored in the <Application_Home>/tmp directory. Although these files are not backed up to iCloud, remember to delete those files when you are done with them so that they do not continue to consume space on the user’s device.
Use the "do not back up" attribute for specifying files that should remain on device, even in low storage situations. Use this attribute with data that can be recreated but needs to persist even in low storage situations for proper functioning of your app or because customers expect it to be available during offline use. This attribute works on marked files regardless of what directory they are in, including the Documents directory. These files will not be purged and will not be included in the user's iCloud or iTunes backup. Because these files do use on-device storage space, your app is responsible for monitoring and purging these files periodically.
iOS Data Storage Guidelines -> https://developer.apple.com/icloud/documentation/data-storage/index.html
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