View controllers are instances of a subclass of UIViewController. A view controller manages a view hierarchy. It is responsible for creating the view objects that make up the hierarchy and for handling events associated with the view objects in its hierarchy.

So far, WorldTrotter has a single view controller that displays some labels. In this chapter, you will update the app to use multiple view controllers. The user will be able to switch between two view hierarchies – one for the existing temperature conversion screen and another for a map (Figure 4.1).

Figure 4.1  The two faces of WorldTrotter