iOS 9 project demonstrating the use of a UIActivityViewController on iPhone and iPad
I'm explaining the code here: http://pinkstone.co.uk/how-to-share-things-with-a-uiactivityviewcontroller/
Updated with NSPhotoLibraryUsageDescription as required by iOS 10. I've explained how to do this here: http://pinkstone.co.uk/what-is-the-nsphotolibraryusagedescription-key/