What are Anchor and Passthrough used for in popover segues?
These are properties of the
UIPopoverController, not the segue. Thats why if you look at the documentation for the
UIStoryboardPopoverSegue, you won't find these two properties.
The anchor is telling the
UIPopoverController where to point its arrow.
The passthrough is an array of views that the user can interact with while the
UIPopoverController is displayed.
The documentation is here: https://developer.apple.com/documentation/uikit/uipopovercontroller
and the section going over the passthrough views is here:https://developer.apple.com/documentation/uikit/uipopovercontroller/1624654-passthroughviews