Protocols, Delegates and Functions.
I've been browsing through the Apple Swift resources and stumbled upon a pretty good example on Document Management (some good cloud usage samples as well). I'm working quite a bit with 'Document' files both on iOS and OS X and wondered whether the samples provided could be extended into an application framework shared across a suite of products (you should only write code once).
You'll find the Apple resources here, well worth a browse around.
I'll just put the playground code up here showing results of my research - I think it's fairly self explanatory.
I think it leads to more concise code personally - I'd appreciate your thoughts.