Open Radar

 
Summary:
UIDocumentInteractionController silently fails to Open In… when there are no apps on the device that can handle the given file type. There is no mechanism to detect this situation.

Steps to Reproduce:
1. Build and run the attached app on a clean device.
2. In the picker control, choose Email, a file type for which there is an installed app (Notes) with which to open it.
3. Click the last button on the screen, "Share with UIDocumentInteractionController Open In…"
4. Notice that a sheet appears to let you choose an app.
5. Cancel.
6. In the picker control, choose Acorn, a file type for which there are no installed apps with which to open it.
7. Click the last button on the screen, "Share with UIDocumentInteractionController Open In…"

Expected Results:
A sheet appears telling the user that no apps are available

Actual Results:
Nothing happens

Regression:
Not a regression. This problem also existed in iOS 8.

Notes:
An (even better) alternative would be to provide an API on UIDocumentInteractionController so that we can query for the presence of any apps that can open a given file type. If we had that, then we could disable our "Open In…" button when tapping it would do nothing..