Making Apps with Core Data

Modeling data

• Model explorer? an box diagram type viewer
• Attributes and relationships
• Cascade and other deletion rules
• Classes
  • Model: ManagedObjectModel
  • Store coordinator: PersistentStoreCoordinator
    • Usually manages a db on the filesystem,
  • Context: ManagedObjectContext
    • Need this to get anything done
  • All three contained in a PersistentContainer
    • easily created via model name
    • container.loadPersistenStores()
  • Contexts:
    • Query generations provide stability, set to .current
    • automaticcally merges changes from parent = true
    • Should do all data work on a context queue
      • performAndWait, perform, performBackgroundTask
  • Data
    • Can init objects, and save to create them.
    • But if you need a lot more, batch insertions.

Controllers

• Fetching
  • Fetch requests get objs from a store. with predicates.
  • Can use KVO on these ManagedObjects with views
  • Can set sort descriptors
  • Can set batch size, limits
  • Fetch results controller, for basically streaming results as the load and update. For table views basically
• Denormalization
  • when we keep copys of data to make access more efficient. like db indexes
  • DerivedAttributes. Normalized metadata maintained for you by core data.
  • Supports duplication, transformation (lowercase etc), aggregates like count, zero param functions (now())

Scaling

• Fetching persistent history changes
• How to know when other coordinators change the store
  • Remote Change Notifications
  • turn on with a persistent change option
  • and turn on persistent history
• Use the sanitizers