Controllers of Controllers in iOS

In iOS there are some constructs built into the system to enable controlling a bunch of controllers.

UINavigationController

• Has property 'rootViewController' that points to another MVC.  The rootViewController controls which view is displayed in the "Custom content" area.
• Performing a segue to push a new MVC's view onto screen, other one slides off the screen.  When the segue is completed the new view has a back button in the Navigation Bar at top.  When click the back button you pop the current view off the navigation stack and, generally, remove it from the heap.  Those earlier views/mvc's remain in the heap.
• segues always create a new view controller