Using view controller composition

As we have seen in this section, composing view controllers is a powerful design pattern that will help you do the following:

This pattern can be used programmatically or with storyboards. When using this pattern with storyboards, the interface builder lets you reference controllers that are declared in any storyboard of your project. You should prefer the method of splitting your controllers and storyboards, as loading large storyboards can have a dramatic impact on performance at development time or runtime.