Core Data Fundamentals - @ajithrnayak 

Core Data Vs Developers 

Core Data Stack NSPersistentStoreCoordinator SQLite NSPersistentContainer NSManagedObjectContext NSPersistentStore NSManagedObjectModel App 

NSManagedObjectContext • Like a scratchpad • fetch, change, add and delete • Create more than one contexts • Updates persistent store 

Concurrency policies ConcurrencyType NSPrivateQueueConcurrencyType 
 (background queue) NSMainQueueConcurrencyType 
 (application’s main queue) 

perform(_:) • asynchronous method • gets wrapped in a autorelease pool. performAndWait(_:) • synchronous method • will block the calling thread • does not wrap the block in an 
 autorelease pool. 

Summary • A managed object context is tied to a serial queue. • Create only two contexts for simplicity. • Concurrency types are two but contexts can be many. • Context executes on a “private” queue. • Performance heavy operations should be performed on the background queue. • Don’t pass NSManagedObject instances between queues. • To avoid unnecessary saves, be aware of automatically triggered broadcasts. 

Thank you