Document provider extensions in iOS 8 are part of the new Extensibility system and allow the features from Document Picker and associated file handling to go beyond iCloud Drive to encompass enterprise storage and popular online services like DropBox, Box, OneDrive, Google Drive, and more. Because it ties into the same system and works the same way, as long as they implement the extension, Apple's making it just as easy to use anyone else's online storage as it is to use iCloud Drive. So, how does it work?
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