This chapter wraps up your exploration of protocol-oriented programming, value types, and reference types. In the previous two chapters, you saw some hypothetical situations that explain the power of these features in Swift. This chapter tied it all together by applying your newfound knowledge to the Hello-Contacts app you worked on before. You now know how you can bump up the quality of your code and future-proof an existing application by implementing protocols. To implement protocols, you have to improve your application structure by making sure that ViewController didn't contain too much functionality. This in itself was a vast improvement that you were able to take to the next level with a protocol.

Now that you have explored some of the best practices of Swift and applied them to an existing app, it's time to deep dive into Core Data. The next chapters outline how Core Data works and how you can take advantage of it in your applications. If all this value type and protocol-oriented programming talk has made your head reel, don't worry. Take some time to review this chapter and to experiment. The best way to learn these principles is by practicing.