Chapter 19
Working with Core Data

Learn not to add too many features right away, and get the core idea built and tested.

– Leah Culver

Congratulations on making it this far! By now you've already built a simple app for users to list their favorite restaurants. If you've worked on the previous exercise, you should understand the fundamentals of how to add a restaurant; I've tried to keep things simple and focus on the basics of UITableView. Up to this point, all restaurants have been predefined in the source code and stored in an array. If you want to add a restaurant, the simplest way is to append the new restaurant to the existing restaurants array.

However, if you do it that way, you can't save the new restaurant permanently. Data stored in memory (e.g. array) is volatile. Once you quit the app, all the changes are gone. We need to find a way to save the data in a persistent manner.

To save the data permanently, we'll need to save in a persistent storage-like file or database. By saving the data to a database, for example, the data will be safe even if the app quits or crashes. Files are another way to save data, but they are more suitable for storing small amounts of data that do not require frequent changes. For instance, files are commonly used for storing application settings like the Info.plist file.

The FoodPin app may need to store thousands of restaurant records. Users may also add or remove the restaurant records quite frequently. In this case, a database is a suitable way to handle a large set of data. In this chapter, I will walk you through the Core Data framework and show you how to use it to manage data in the database. You will make a lot of changes to your existing FoodPin project, but after going through this chapter your app will allow users to save their favorite restaurants persistently.

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