How to show “Open In…” when a user tries to open email attachments in iOS
问题 I've seen some iOS apps have this function: When a user tries to open an email attachment, they can press and hold on the attachment for a couple of seconds, and a popup menu will appear displaying two buttons. One button reads "Open in iBooks" (for example). When user clicks it, then the app will be run and open the attachment. I would like to know how to register my application to be associated with a particular document type. Also what happens to the document when it is opened? Is it