This chapter was all about adding a small, simple feature to an existing app. We added the ability to load real data from an API. You saw that networking is made pretty straightforward by Apple with URLSession and data tasks. You also learned that this class abstracts away some very complex behavior regarding multithreading, so your apps remain responsive while data is loaded from the network. Next, you implemented a helper struct for networking and updated the Core Data model to store ratings for movies. Once all this was done, you could finally see how multithreading worked in the context of this app. This wasn't everything we needed to do, though. You learned about ATS and how it keeps your users secure. You also learned that you sometimes need to circumvent ATS, and we covered how you can achieve this.

Even though the feature itself wasn't very complex, the concepts and theory involved can be quite overwhelming. You suddenly had to deal with code that would be executed asynchronously in the future. And not just that. The code even used multiple threads to make sure that its performance was optimal. The concepts of multithreading and asynchronous programming are arguably two of the more complex aspects of programming. Practice them a lot and try to remember that any time you're passing around a closure, you could be writing some asynchronous code that gets executed on a different thread.

Now that the list of movies is updated with data from the web, let's take it one step further in the next chapter. You can use background-fetching to make sure that you always fetch the most up-to-date information for movies and update them without the user even noticing.