The document discusses Core Data, an object graph and persistence framework for managing and persisting data in iOS and macOS applications. It provides an overview of why and when to use Core Data, noting that it handles common tasks like data schema changes, syncing with servers and peers, undo/redo, threading, and notifying code of changes. It also discusses alternatives like MagicalRecord that simplify Core Data usage. The document recommends using Core Data for any non-trivial application where requirements may change over time, and provides code examples for common Core Data tasks like fetching, saving context, and queries.

1. Tomáš Jukin
@Inza
Core Data
there is an ORM you can like!

3. Core Data?

4. Core Data?
-- It’s a big hairy mess!

5. Core Data?
-- It’s a big hairy mess!
YES! but Why?

6. Core Data?
-- It’s a big hairy mess!
YES! but Why?
Real problems are hard.

7. Core Data?
-- It’s a big hairy mess!
YES! but Why?
Real problems are hard. Really?

8. Core Data?
-- It’s a big hairy mess!
YES! but Why?
Real problems are hard. Really? Really.

9. Core Data?
-- It’s a big hairy mess!
YES! but Why?
Real problems are hard. Really? Really.
CoreData is hairy

10. Core Data?
-- It’s a big hairy mess!
YES! but Why?
Real problems are hard. Really? Really.
CoreData is hairy
because it ...

11. Core Data?
-- It’s a big hairy mess!
YES! but Why?
Real problems are hard. Really? Really.
CoreData is hairy
because it ...
... solves real problems!

12. Tomáš Jukin
@Inza
www.juicymo.cz
@JuicymoCZ

13. 1) WHY and WHEN to
use Core Data?

14. 1) WHY and WHEN to
use Core Data?
2) HOW to use Core
Data?

15. WHY?

16. 1) Death

17. 1) Death
2) Taxes

18. 1) Death
2) Taxes
3) SW Requirements
WILL change

19. “Do you understand how to
structure real-world data
access for Mac and iOS
applications better than
Apple?”

20. “Do you understand how to
structure real-world data
access for Mac and iOS
applications better than
Apple?”
-- Nope.

21. • Handling future changes to the data
schema
• Bi-directional sync with servers
• Bi-directional sync with peers (e.g. iPad <-> iPhone)
• Undo - Redo
• Multithreading long-running operations
• Sync data between multiple threads
• Notifying faraway code about changes to
objects so that they can refresh or
update at appropriate intervals
Has your own so-called
“data stack” features like this?

22. Do I need these features?
(= WHEN?)

23. But if...
I NEVER update my app!
My users NEVER do mistakes!
I NEVER use threads!
My app is just one view!
My data operations ARE all instantaneous!
Requirements of my apps NEVER changes!

24. 1) Death
2) Taxes
3) SW Requirements
WILL change

25. ... all of that is TRUE for you
Core Data is NOT for you.

26. ... all of that is TRUE for you
Core Data is NOT for you.
Otherwise you
SHOULD use it.

27. Core Data =
Do not implement
Do not test
Do not optimize

28. Core Data =
Do not implement
Do not test
Do not optimize
Data Stack code used by your app!
Apple has already done
that!

29. Fact
Apple’s high-level APIs can
be much faster than YOUR
“optimized” code at lower
levels

30. Fact
Example:
Fast Image? ➜
UIImageView

31. Fact
CoreData
is
Cocoa
for Models

32. Cocoa for Models
Is UIButton easy?
Is UITableView easy?
Is Delegation Pattern easy?
Is InterfaceBuilder and
outlets easy?

33. Cocoa for Models
Is UIButton easy?
Is UITableView easy?
Is Delegation Pattern easy?
Is InterfaceBuilder and
outlets easy?
NOPE!

34. Cocoa for Models
Are they powerful?

35. Cocoa for Models
Are they powerful?
YES!

36. Why NOT to use Core Data?
•Programmer naivity

37. •Programmer naivity
➜ “My app isn’t complex enought”
= I am too lazy to learn it
Why NOT to use Core Data?

38. •Programmer naivity
➜ “My app isn’t complex enought”
= I am too lazy to learn it
➜ “I dont like large frameworks - I used them
in HALF of my app and it was so much work!”
= Use entirely it or not. Otherwise it will
not save time & effort
Why NOT to use Core Data?

39. •Programmer naivity
➜ “My app isn’t complex enought”
= I am too lazy to learn it
➜ “I dont like large frameworks - I used them
in HALF of my app and it was so much work!”
= Use entirely it or not. Otherwise it will
not save time & effort
•Willful ignorance
Why NOT to use Core Data?

40. •Programmer naivity
➜ “My app isn’t complex enought”
= I am too lazy to learn it
➜ “I dont like large frameworks - I used them
in HALF of my app and it was so much work!”
= Use entirely it or not. Otherwise it will
not save time & effort
•Willful ignorance
➜ “I don’t have any idea what I’m talking
about, but it sounds like a bad idea to me”
= What?
Why NOT to use Core Data?

41. So?
Reading code is hard
Writing code is easy
Why learn when we can re-invent?
Really? If this works in your world,
Core Data is not for you...

42. OK, but when seriously NO?
Update HUGE part of DB in one
moment
Working with lots of records
➜ RSS Reader app

43. Still not ready to use Core Data?
Read this:
goo.gl/Flzrsk
Numbers here:
goo.gl/lNFjdr

44. HOW?

45. .sqlite
Schema
App

46. .sqlite
ORM Schema
App

47. .sqlite
App
Core Data Schema
App
.sqlite
Web
Store

48. .sqlite
App
Schema
App
.sqlite
Web
Store
NSManaged
ObjectContext
NSManaged
ObjectContext
NSManaged
ObjectModel
Persistent
ObjectStore
Persistent
ObjectStore
Persistent
ObjectStore
Persistent
Store Coordinator

49. .sqlite
App
Schema
App
.sqlite
Web
Store
NSManaged
Object
NSManaged
Object
NSManaged
Object
NSManaged
ObjectContext
NSManaged
ObjectContext
NSManaged
ObjectModel
Persistent
ObjectStore
Persistent
ObjectStore
Persistent
ObjectStore
Persistent
Store Coordinator

50. ...Complex ORM
=> Complex Setup

51. Setup

52. // In the AppDelegate.h
@property (readonly, strong, nonatomic) NSManagedObjectContext
*managedObjectContext;
@property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel;
@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator
*persistentStoreCoordinator;
- (void)saveContext;
- (NSURL *)applicationDocumentsDirectory;
// In the AppDelegate.m
- (void)applicationWillTerminate:(UIApplication *)application
{
// Saves changes in the application's managed object context before the application terminates.
[self saveContext];
}
- (void)saveContext
{
NSError *error = nil;
NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
if (managedObjectContext != nil)
{
if ([managedObjectContext hasChanges] &amp;&amp; ![managedObjectContext
save:&amp;error])
{
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
}
}
#pragma mark - Core Data stack
/**
Returns the managed object context for the application.
If the context doesn't already exist, it is created and bound to the persistent store coordinator for the
application.
*/
- (NSManagedObjectContext *)managedObjectContext
{
if (__managedObjectContext != nil)
{
return __managedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil)
{
__managedObjectContext = [[NSManagedObjectContext alloc] init];
[__managedObjectContext setPersistentStoreCoordinator:coordinator];
}
return __managedObjectContext;
}
/**
Returns the managed object model for the application.
If the model doesn't already exist, it is created from the application's model.
*/
- (NSManagedObjectModel *)managedObjectModel
{
if (__managedObjectModel != nil)
{
return __managedObjectModel;
}
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"blaba"
withExtension:@"momd"];
__managedObjectModel = [[NSManagedObjectModel alloc]
initWithContentsOfURL:modelURL];
return __managedObjectModel;
}
/**
Returns the persistent store coordinator for the application.
If the coordinator doesn't already exist, it is created and the application's store added to it.
*/
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
if (__persistentStoreCoordinator != nil)
{
return __persistentStoreCoordinator;
}
NSURL *storeURL = [[self applicationDocumentsDirectory]
URLByAppendingPathComponent:@"blaba.sqlite"];
NSError *error = nil;
__persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc]
initWithManagedObjectModel:[self managedObjectModel]];
if (![__persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType
configuration:nil URL:storeURL options:nil error:&amp;error])
{
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
return __persistentStoreCoordinator;
}
#pragma mark - Application's Documents directory
/**
Returns the URL to the application's Documents directory.
*/
- (NSURL *)applicationDocumentsDirectory
{
return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory
inDomains:NSUserDomainMask] lastObject];
}

53. 99 rows!

54. Really ?!

55. Core Data bites!

56. The Cure
1) MagicalRecord
github.com/magicalpanda/MagicalRecord

57. The Cure
1) MagicalRecord
github.com/magicalpanda/MagicalRecord
2) Mogenerator
github.com/rentzsch/mogenerator

58. The Cure
1) MagicalRecord
github.com/magicalpanda/MagicalRecord
2) Mogenerator
github.com/rentzsch/mogenerator
+ CocoaPods (as usual)

59. Magical Record

60. Magical Record
Nice (Rails like) API
on Core Data

61. Magical Record
Nice (Rails like) API
on Core Data
You still can dive in!

62. // In the AppDelegate.h
@property (readonly, strong, nonatomic) NSManagedObjectContext
*managedObjectContext;
@property (readonly, strong, nonatomic) NSManagedObjectModel *managedObjectModel;
@property (readonly, strong, nonatomic) NSPersistentStoreCoordinator
*persistentStoreCoordinator;
- (void)saveContext;
- (NSURL *)applicationDocumentsDirectory;
// In the AppDelegate.m
- (void)applicationWillTerminate:(UIApplication *)application
{
// Saves changes in the application's managed object context before the application terminates.
[self saveContext];
}
- (void)saveContext
{
NSError *error = nil;
NSManagedObjectContext *managedObjectContext = self.managedObjectContext;
if (managedObjectContext != nil)
{
if ([managedObjectContext hasChanges] &amp;&amp; ![managedObjectContext
save:&amp;error])
{
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
}
}
#pragma mark - Core Data stack
/**
Returns the managed object context for the application.
If the context doesn't already exist, it is created and bound to the persistent store coordinator for the
application.
*/
- (NSManagedObjectContext *)managedObjectContext
{
if (__managedObjectContext != nil)
{
return __managedObjectContext;
}
NSPersistentStoreCoordinator *coordinator = [self persistentStoreCoordinator];
if (coordinator != nil)
{
__managedObjectContext = [[NSManagedObjectContext alloc] init];
[__managedObjectContext setPersistentStoreCoordinator:coordinator];
}
return __managedObjectContext;
}
/**
Returns the managed object model for the application.
If the model doesn't already exist, it is created from the application's model.
*/
- (NSManagedObjectModel *)managedObjectModel
{
if (__managedObjectModel != nil)
{
return __managedObjectModel;
}
NSURL *modelURL = [[NSBundle mainBundle] URLForResource:@"blaba"
withExtension:@"momd"];
__managedObjectModel = [[NSManagedObjectModel alloc]
initWithContentsOfURL:modelURL];
return __managedObjectModel;
}
/**
Returns the persistent store coordinator for the application.
If the coordinator doesn't already exist, it is created and the application's store added to it.
*/
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
if (__persistentStoreCoordinator != nil)
{
return __persistentStoreCoordinator;
}
NSURL *storeURL = [[self applicationDocumentsDirectory]
URLByAppendingPathComponent:@"blaba.sqlite"];
NSError *error = nil;
__persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc]
initWithManagedObjectModel:[self managedObjectModel]];
if (![__persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType
configuration:nil URL:storeURL options:nil error:&amp;error])
{
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
return __persistentStoreCoordinator;
}
#pragma mark - Application's Documents directory
/**
Returns the URL to the application's Documents directory.
*/
- (NSURL *)applicationDocumentsDirectory
{
return [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory
inDomains:NSUserDomainMask] lastObject];
}
CD

63. 99 rows!

64. - (BOOL)application:(UIApplication *)application
didFinishLaunchingWithOptions:(NSDictionary *)
launchOptions
{
[MagicalRecord
setupCoreDataStackWithStoreNamed:
@"MyDatabase.sqlite"];
// ...
return YES;
}
- (void)applicationWillTerminate:(UIApplication *)
application
{
[MagicalRecord cleanUp];
}
MR

65. 11 rows!

66. Fetch

67. NSArray
*fetchedObjects;
NSManagedObjectContext
*context
=
[self
managedObjectContext];
NSFetchRequest
*fetch
=
[[NSFetchRequest
alloc]
init];
NSEntityDescription
*entityDescription
=
[NSEntityDescription
entityForName:@"Person"
inManagedObjectContext:context];
[fetch
setEntity:entityDescription];
[fetch
setPredicate:[NSPredicate
predicateWithFormat:@"age
=
%d",
25]];
NSError
*error
=
nil;
fetchedObjects
=
[context
executeFetchRequest:fetch
error:&error];
if([fetchedObjects
count]
==
1)
return
[fetchedObjects
objectAtIndex:0];
else
return
nil;
CD

68. NSArray
*fetchedObjects;
NSManagedObjectContext
*context
=
[self
managedObjectContext];
NSFetchRequest
*fetch
=
[[NSFetchRequest
alloc]
init];
NSEntityDescription
*entityDescription
=
[NSEntityDescription
entityForName:@"Person"
inManagedObjectContext:context];
[fetch
setEntity:entityDescription];
[fetch
setPredicate:[NSPredicate
predicateWithFormat:@"age
=
%d",
25]];
NSError
*error
=
nil;
fetchedObjects
=
[context
executeFetchRequest:fetch
error:&error];
if([fetchedObjects
count]
==
1)
return
[fetchedObjects
objectAtIndex:0];
else
return
nil;
CD

69. [Person findByAttribute:@"age"
withValue:@25];
MR

70. // Query to find all the persons store into the database
NSArray *persons = [Person MR_findAll];
// Query to find all the persons store into the database order by their
'firstname'
NSArray *personsSorted =
[Person MR_findAllSortedBy:@"firstname"
ascending:YES];
// Query to find all the persons store into the database which have 25
years old
NSArray *personsWhoHave22 =
[Person MR_findByAttribute:@"age"
withValue:[NSNumber numberWithInt:25]];
// Query to find the first person store into the databe
Person *person = [Person MR_findFirst];
MR

71. // Query to find all the persons store into the database
NSArray *persons = [Person MR_findAll];
// Query to find all the persons store into the database order by their
'firstname'
NSArray *personsSorted =
[Person MR_findAllSortedBy:@"firstname"
ascending:YES];
// Query to find all the persons store into the database which have 25
years old
NSArray *personsWhoHave22 =
[Person MR_findByAttribute:@"age"
withValue:[NSNumber numberWithInt:25]];
// Query to find the first person store into the databe
Person *person = [Person MR_findFirst];
MR

72. // Query to find all the persons store into the database
NSArray *persons = [Person findAll];
// Query to find all the persons store into the database order by their
'firstname'
NSArray *personsSorted =
[Person findAllSortedBy:@"firstname"
ascending:YES];
// Query to find all the persons store into the database which have 25
years old
NSArray *personsWhoHave22 =
[Person findByAttribute:@"age"
withValue:[NSNumber numberWithInt:25]];
// Query to find the first person store into the databe
Person *person = [Person findFirst];
MR

73. Background Op

74. [MagicalRecord
saveWithBlock:^(NSManagedObjectContext
*localContext)
{
Post
*post
=
[Post
createInContext:localContext];
//
photo
processing
//
update
post
from
photo
processing
}
completion:^(BOOL
success,
NSError
*error)
{
//
This
is
called
when
data
done,
//
and
is
called
on
the
main
thread
}];
MR

75. Mogenerator

76. Mogenerator
Because Xcode sucks!

77. Mogenerator
Because Xcode sucks!
_User for machine
User for human

78. Mogenerator
Because Xcode sucks!
_User for machine
User for human
+ auto regen!

79. But the docs sucks too!
It coves the basics, but I DO NEED to DIVE in!
goo.gl/9fNe0z
goo.gl/durEGR

80. Recap
•You want to use Core Data
•You want to use NSFetchResultsController
•You want to use MagicalRecord
•You want to use Mogenerator
•YOP, setup of that is epic!
•You want to use CocoaPods
•YOP, docs for CoreData and MagicalRecord
sucks
LET the CoreData work for you!

81. For-Mobile
http://srazy.info/for-mobile
Pondělí, 24. 3. 2014 19:00
Jakub Hladík
Automatic builds for iOS
=> Tomorrow!
=> AfterPUB included!

82. Tomáš Jukin
@Inza
www.juicymo.cz
@JuicymoCZ

83. Tomáš Jukin
@Inza
www.juicymo.cz@JuicymoCZ
goo.gl/jGLovj

84. Photo Credits
All photos used are CC from Flickr
http://www.flickr.com/photos/
60256070@N05/8330184193/