A small and quick introduction to Core Data on the iPhone.

1. Introduction to
Core Data
Daniel Tull

2. Sky+ Little Spender
Weather Maps Fourgy

3. Core Data Stack
NSManagedObjectModel

4. Managed Object Model

5. Attributes
NSNumber
NSString Transformable
BOOL You put in code to
transform the
NSDate
object or value into
NSData a compatible type.
Transformable

6. Relationships
Properties that reference other objects
Can be to-one or to-many (NSSet - unordered)
Can (and should) have inverses, which are worked
out by Core Data when you set the other property
Delete rule ensures propagation

7. Relationships
DTAlbum
Attributes
DTArtist name
DTGenre Attributes discCount
Attributes name trackCount
name Relationships Relationships
Relationships albums artist
artists genres composers
songs songs songs

8. Core Data Stack
NSManagedObjectContext
NSPersistentStoreCoordinator NSPersistentStore
NSManagedObjectModel

9. Create and Save Objects
DTSong *song = [NSEntityDescription
insertNewObjectForEntityForName:@“DTSong”
inManagedObjectContext:managedObjectContext];
DTArtist *artist = [NSEntityDescription
insertNewObjectForEntityForName:@“DTArtist”
inManagedObjectContext:managedObjectContext];
artist.name = @“Moby”;
song.title = @“Porcelain”;
song.artist = artist;
•••
NSError *error = nil;
[managedObjectContext save:&error];

10. Create and Save Objects
NSManagedObjectContext
DTArtist
DTSong
NSPersistentStoreCoordinator NSPersistentStore
NSManagedObjectModel

11. Fetching Objects
All songs by “La Roux” sorted by title.
Entity DTSong
Predicate @“artist.name == %@”, @“La Roux”
Sorting @“title”

12. Fetching Objects
Fetch all playlists which contain more than an hour of music.
Entity DTPlaylist
Predicate @“@sum.songs.duration > 3600”
Sorting @“name”

13. Fetching Objects
NSEntityDescription *entity = [NSEntityDescription
entityForName:@“DTSong”
inManagedObjectContext:managedObjectContext];
NSPredicate *predicate = [NSPredicate
predicateWithFormat:@“artist.name == %@”, @“La Roux”];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc]
initWithKey:@“title” ascending:YES];
NSArray *descriptors = [NSArray arrayWithObject:sortDescriptor];
NSFetchRequest *request = [[NSFetchRequest alloc] init];
[request setEntity:entity];
[request setPredicate:predicate];
[request setSortDescriptors:sortDescriptors];
NSArray *fetchResult = [managedObjectContext executeFetchRequest:request
error:&error];

14. Fetching Objects
NSManagedObjectContext NSFetchRequest
DTArtist DTSong
DTSong
DTSong DTSong
NSPersistentStoreCoordinator NSPersistentStore
DTSong
NSManagedObjectModel DTSong
DTSong

15. Performance: Faults
Faults are placeholders for related objects, which
mean you don’t use memory on unwanted objects.
DTSong
DTSong
DTArtist DTSong
DTSong
DTSong

16. Performance: Batching
DTArtist
DTArtist
Batching allows
you to bring only a DTArtist
subset of objects DTArtist
into memory.
DTArtist
DTArtist

17. Demo

18. DTMusicModel
hg.danieltull.co.uk/dtmusicmodel

19. DTGridView DTSwapView
hg.danieltull.co.uk/dtkit

20. Thank You
dt@danieltull.co.uk
hg.danieltull.co.uk