Called after the view controller is added or removed from a container view controller.
- iOS 5.0+
- tvOS 9.0+
The parent view controller, or
nilif there is no parent.
Your view controller can override this method when it wants to react to being added to a container.
If you are implementing your own container view controller, it must call the
did method of the child view controller after the transition to the new controller is complete or, if there is no transition, immediately after calling the
remove method automatically calls the
did method of the child view controller after it removes the child.