Understanding how saving and loading works

Let's review what you have done so far. You have created Review and RestaurantPhoto entities using the data model editor, and you have created the corresponding model objects for them, named ReviewItem and RestaurantPhotoItem. You created the CoreDataManager class to add and get Review and RestaurantPhoto instances from the persistent store. The CoreDataManager class uses the restaurant identifier to associate reviews and restaurant photos with a specific restaurant, but where does it come from?

Open the Misc folder in your project, and open the JSON folder. If you click on any one of the JSON files inside, you'll see that each restaurant has a unique numeric identifier. For example, the identifier for The Tap Trailhouse restaurant is 145237, as shown in the screenshot below:

Figure 21.12: Editor area showing contents for Boston.json

When you save restaurant photos and reviews to the persistent store,...