Most modern applications communicate with a web service. Some apps rely on them heavily, acting as a layer that merely reads data from the web and displays it in app form. Other apps use the web to retrieve and sync data to make it locally available, and others only use the web as backup storage. Of course, there are a lot more reasons to use data from the internet than the ones mentioned.

In this chapter, you will expand the MustC application, so it uses a web service to retrieve popularity ratings for the movies that family members have added as their favorites. These popularity ratings will be stored in the Core Data database and displayed together with the names of the movies.

In this chapter, you'll learn about the following topics:

URLSession
Working with JSON in Swift
Updating Core Data objects with fetched data