I looked into presenting action sheets and activity view controllers, and wrote about some unexpected things I found: pspdfkit.com/blog/2016/popovers-on-popovers/
It all started with this twitter.com/steipete/status/755409285111218180
Then I saw this and couldn’t reproduce it. twitter.com/jesse_squires/status/755415278658334721
Eventually found reading a property changed behaviour, so I wrote a Radar. openradar.appspot.com/27448488
And in the end I could not reproduce what Pages did, so another Radar. openradar.appspot.com/27448912