UIPopoverController and Modal View Controllers - iOS Programming: The Big Nerd Ranch Guide - page 419

swap in the views of the view controllers it contains. Any UIViewController can
present another view controller modally.
Figure 13.7 Presenting-presenter relationship
There are two built-in properties for managing the relationship between presenter and
presentee. A modally-presented view controller's presentingViewController will
point back to the view controller that presented it, while the presenter will keep a pointer
to the presentee in its presentedViewController property ( Figure 13.7 ).
Inter-family relationships
A presented view controller and its presenter are not in the same view controller family.
Instead, the presented view controller has its own family. Sometimes, this family is just
one UIViewController ; other times, this family is made up of multiple view control-
lers.
Understanding the difference in families will help you understand the values of properties
like presentedViewController and navigationController . Consider the
view controllers in Figure 13.8 . There are two families, each with multiple view control-
lers. This diagram shows the values of the view controller relationship properties.