Persistent store coordinator
A persistent store coordinator associates persistent object stores and a managed object model, and presents a facade to managed object contexts such that a group of persistent stores appears as a single aggregate store. A persistent store coordinator is an instance of
NSPersistentStoreCoordinator. It has a reference to a managed object model that describes the entities in the store or stores it manages.
The coordinator is the central object in a Core Data stack. In many applications you just have a single store, but in complex applications there may be several, each potentially containing different entities. The persistent store coordinator’s role is to manage these stores and present to its managed object contexts the facade of a single unified store. When you fetch records, Core Data retrieves results from all of them, unless you specify which store you’re interested in.