UIPopoverPresentationController

UIPopoverPresentationController is the new (as of iOS 8) way to do a popover. This replaces the older UIPopoverController, and should be used for anything recent.

Arrow Directions

If you only ever want to show your popover from a given direction, you can control this with the permittedArrowDirections property. According to the documentation, you can only do this when configuring, not after it’s been presented1. As the name suggests, this controls where the arrow on the popover shows, not where the popover is relative to the sourceRect/sourceView.

When the device rotates

You can also control where the popover comes from by updating the sourceRect/sourceView. This can be done after receiving viewWillTransition(to:with:) on the presenting view controller. Be sure to call view.layoutIfNeeded() on the presenting view controller before updating this, otherwise the sourceRect might be outdated2.

1

I haven’t tested this myself to see what happens if you do try to change that property after it’s been presented.

2

I’m unsure if you have to call layoutIfNeeded() if you use sourceView instead of sourceRect.