Understanding Core Data framework classes

The following diagram illustrates a simplified, conceptual schema of the relationship among the main objects that are part of the Core Data stack:

Figure 12.1 – A Core Data simplified conceptual stack

If you are unfamiliar with UML notation, the diamond means “contains” or “has-a.” In a UML object diagram, the upper part of the rectangle represents the object type, the middle part its properties, and the lower part its methods. A minus sign represents instance properties and methods, while a plus sign represents static or class methods and properties.

Here is a description of the main classes that are the components of Core Data:

• NSManagedObjectModel: This class represents the data model of an application, essentially a database schema for all the entities, attributes, and relationships that a Core Data store contains. This model is usually created and edited using...