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Apple's Document-Based App Programming Guide for iOS shows example code that builds a list of FileRepresentation objects to show a document index. No instances of UIDocument are created initially. Then, when a document is opened, the UIDocument subclass instance is created. The most the guide says about this design is:

The example application now has an array (_fileList) of custom model objects that encapsulate the name and file URL of each of the application’s documents. (FileRepresentation is the custom class of those objects.)

See https://developer.apple.com/library/ios/documentation/DataManagement/Conceptual/DocumentBasedAppPGiOS/ManageDocumentLifeCycle/ManageDocumentLifeCycle.html#//apple_ref/doc/uid/TP40011149-CH4-SW8

Why is this FileRepresentation object used instead of just creating a list of UIDocuments? Is there overhead in creating a UIDocument even if it isn't open? What if I want my file chooser to listen for iCloud conflicts (this requires an instance of UIDocument)?

It would be more elegant if I could just store the UIDocument instances in my file list, both for handling iCloud conflicts, and in case the user changes the document name while the document is open.

Taylor
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Why is this FileRepresentation object used instead of just creating a list of UIDocuments?

You could in theory use UIDocument. The reason why they don't in the documentation is that subclasses of UIDocument can be implemented in a way that is memory intense. Creating an object that just manages the name and url is an easy way to ensure low memory usage until you need the rest of the UIDocument class.

Fruity Geek
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