This document discusses various data persistence options in iOS, including NSUserDefaults, NSCache, archives using the NSCoding protocol, Core Data, and iCloud. It provides an overview and examples of each technique. NSUserDefaults is best for small amounts of non-sensitive data. NSCache is useful for caching objects in memory. Archives allow custom objects to be encoded and stored. Core Data provides a full object graph and relationship management system. iCloud syncs data across devices.

1. Data Persistence in iOS
Michał Tuszyński
iOS/Android developer at appvetica
@srgtuszy srgtuszy.github.com

2. Roadmap

3. Roadmap
1. NSUserDefaults

4. Roadmap
1. NSUserDefaults
2. NSCache

5. Roadmap
1. NSUserDefaults
2. NSCache
3. NSCoding protocol

6. Roadmap
1. NSUserDefaults
2. NSCache
3. NSCoding protocol
4. CoreData

7. Roadmap
1. NSUserDefaults
2. NSCache
3. NSCoding protocol
4. CoreData
5. iCloud

8. What are
NSUserDefaults?

9. What are
NSUserDefaults?
Key-value local storage, capable of storing both objects
and primitive data types

10. What should not be stored in
NSUserDefaults?

11. What should not be stored in
NSUserDefaults?
1. Sensitive data

12. What should not be stored in
NSUserDefaults?
1. Sensitive data
2. Heavy objects

13. What should not be stored in
NSUserDefaults?
1. Sensitive data
2. Heavy objects
3. Big amounts of data

14. Demo

15. What if I need a mechanism to cache big
amount of objects?

16. What if I need a mechanism to cache big
amount of objects?
...use NSCache!

17. Why NSCache?

18. Why NSCache?
Similar api to NSMutableDictionary class

19. Why NSCache?
Similar api to NSMutableDictionary class
- (void)setObject:(id)obj forKey:(id)key;
- (void)removeObjectForKey:(id)key;

20. Why NSCache?
Why not just use NSMutableDictionary then?

21. Why NSCache?
Why not just use NSMutableDictionary then?

22. Why NSCache?
Why not just use NSMutableDictionary then?
- NSCache takes care of memory management

23. Why NSCache?
Why not just use NSMutableDictionary then?
- NSCache takes care of memory management
- (void)setObject:(id)obj forKey:(id)key cost:(NSUInteger)num;
- (void)setTotalCostLimit:(NSUInteger)lim;

24. Why NSCache?
Why not just use NSMutableDictionary then?
- NSCache takes care of memory management
- (void)setObject:(id)obj forKey:(id)key cost:(NSUInteger)num;
- (void)setTotalCostLimit:(NSUInteger)lim;
- Will let you know when it disposes data (NSCacheDelegate)

25. Why NSCache?
Why not just use NSMutableDictionary then?
- NSCache takes care of memory management
- (void)setObject:(id)obj forKey:(id)key cost:(NSUInteger)num;
- (void)setTotalCostLimit:(NSUInteger)lim;
- Will let you know when it disposes data (NSCacheDelegate)
- (void)cache:(NSCache *)cache willEvictObject:(id)obj

26. Demo

27. How to store custom objects?

28. How to store custom objects?
Using archives!

29. What are archives?

30. What are archives?
Archives provide a means to convert objects and values
into architecture-independent stream of bytes

31. What are archives?
Archives provide a means to convert objects and values
into architecture-independent stream of bytes
Apple documentation

33. Archives

34. Archives

35. Archives
Keyed archives

36. Archives
Keyed archives

37. Archives
Keyed archives Sequential archives

38. What is the difference?

39. What is the difference?

40. What is the difference?
Sequential archives

41. What is the difference?
Sequential archives
-Encoded from root object
through all interrelated objects

42. What is the difference?
Sequential archives
-Encoded from root object
through all interrelated objects
-Must be decoded in the same
order it was encoded

43. What is the difference?
Sequential archives Keyed archives
-Encoded from root object
through all interrelated objects
-Must be decoded in the same
order it was encoded

44. What is the difference?
Sequential archives Keyed archives
-Encoded from root object -Each object is assigned a key
through all interrelated objects
-Must be decoded in the same
order it was encoded

45. What is the difference?
Sequential archives Keyed archives
-Encoded from root object -Each object is assigned a key
through all interrelated objects
-Must be decoded in the same
order it was encoded
NSArchiver

46. What is the difference?
Sequential archives Keyed archives
-Encoded from root object -Each object is assigned a key
through all interrelated objects
-Must be decoded in the same
order it was encoded
NSArchiver NSKeyedArchiver

47. How to create an archive out of a custom object?

48. How to create an archive out of a custom object?
1.Implement NSCoding protocol inside the object

49. How to create an archive out of a custom object?
1.Implement NSCoding protocol inside the object
- (id)initWithCoder:(NSCoder *)decoder;
- (void)encodeWithCoder:(NSCoder *)encoder;

50. How to create an archive out of a custom object?
1.Implement NSCoding protocol inside the object
- (id)initWithCoder:(NSCoder *)decoder;
- (void)encodeWithCoder:(NSCoder *)encoder;
2. Use one of the NSCoder subclasses to get your archive

51. Demo

53. Core Data

54. CoreData is an efficient framework to manage your object
persistence

55. CoreData is an efficient framework to manage your object
persistence
Main features:

56. CoreData is an efficient framework to manage your object
persistence
Main features:
-Change tracking and undo support

57. CoreData is an efficient framework to manage your object
persistence
Main features:
-Change tracking and undo support
-Relationship between entities maintenance

58. CoreData is an efficient framework to manage your object
persistence
Main features:
-Change tracking and undo support
-Relationship between entities maintenance
-Automatic validation of property values

59. CoreData is an efficient framework to manage your object
persistence
Main features:
-Change tracking and undo support
-Relationship between entities maintenance
-Automatic validation of property values
-Low memory overhead (Faulting)

60. What Core Data is not?

61. What Core Data is not?
-It is not a relational database

62. What Core Data is not?
-It is not a relational database
-It’s not a silver bullet for your code

63. How does it work?

64. How does it work?
Storage

65. How does it work?
Storage

66. How does it work?
Storage
NSPersistentStoreCoordinator

67. How does it work?
Storage
The bridge between the storage
NSPersistentStoreCoordinator and the application

68. How does it work?
Storage
The bridge between the storage
NSPersistentStoreCoordinator and the application

69. How does it work?
Storage
NSManagedObjectModel
The bridge between the storage
NSPersistentStoreCoordinator and the application

70. How does it work?
Storage
NSManagedObjectModel
A collection of data models which
are used in the application
The bridge between the storage
NSPersistentStoreCoordinator and the application

71. How does it work?
Storage
NSManagedObjectModel
A collection of data models which
are used in the application
The bridge between the storage
NSPersistentStoreCoordinator and the application

72. How does it work?
Storage
NSManagedObjectModel
A collection of data models which
are used in the application
The bridge between the storage
NSPersistentStoreCoordinator and the application
NSManagedObjectContext

73. How does it work?
Storage
NSManagedObjectModel
A collection of data models which
are used in the application
The bridge between the storage
NSPersistentStoreCoordinator and the application
Scratchpad which communicates
with
NSManagedObjectContext NSPersistentStoreCoordinator to
save changes

74. NSManagedObjectModel

75. NSManagedObjectModel

76. NSManagedObjectModel
Entity

77. NSManagedObjectModel
Entity
Relationship

78. NSManagedObject

79. NSManagedObject
- Generic class that implements all basic behavior
required by CoreData model object

80. NSManagedObject
- Generic class that implements all basic behavior
required by CoreData model object
- It’s not possible to use regular NSObjects with
Core Data

81. NSManagedObject
- Generic class that implements all basic behavior
required by CoreData model object
- It’s not possible to use regular NSObjects with
Core Data
Can be created using following ways:

82. NSManagedObject
- Generic class that implements all basic behavior
required by CoreData model object
- It’s not possible to use regular NSObjects with
Core Data
Can be created using following ways:
1. Designated initializer

83. NSManagedObject
- Generic class that implements all basic behavior
required by CoreData model object
- It’s not possible to use regular NSObjects with
Core Data
Can be created using following ways:
1. Designated initializer
- (id)initWithEntity:(NSEntityDescription *)entity insertIntoManagedObjectContext:
(NSManagedObjectContext *)context

84. NSManagedObject
- Generic class that implements all basic behavior
required by CoreData model object
- It’s not possible to use regular NSObjects with
Core Data
Can be created using following ways:
1. Designated initializer
- (id)initWithEntity:(NSEntityDescription *)entity insertIntoManagedObjectContext:
(NSManagedObjectContext *)context
2. Static method of NSEntityDescription class

85. NSManagedObject
- Generic class that implements all basic behavior
required by CoreData model object
- It’s not possible to use regular NSObjects with
Core Data
Can be created using following ways:
1. Designated initializer
- (id)initWithEntity:(NSEntityDescription *)entity insertIntoManagedObjectContext:
(NSManagedObjectContext *)context
2. Static method of NSEntityDescription class
+ (id)insertNewObjectForEntityForName:(NSString *)entityName inManagedObjectContext:
(NSManagedObjectContext *)context

86. Create NSManagedObjects to represent your data model
NSManagedObject
NSManagedObject
NSManagedObject

87. NSManagedObjects are held in
NSManagedObjectContext’s cache
NSManagedObject
NSManagedObject
NSManagedObject

88. NSManagedObjects are held in
NSManagedObjectContext’s cache
NSManagedObject
NSManagedObject
NSManagedObject

89. NSManagedObjects are held in
NSManagedObjectContext’s cache
NSManagedObject
NSManagedObject NSManagedObjectContext
NSManagedObject

90. NSManagedObjects are held in
NSManagedObjectContext’s cache
NSManagedObject
NSManagedObject NSManagedObjectContext
NSManagedObject

91. NSManagedObjects are held in
NSManagedObjectContext’s cache
NSManagedObject
NSManagedObject NSManagedObjectContext
NSManagedObject
Save

92. Demo

94. iCloud

95. Why should you use iCloud
APIs?

96. Why should you use iCloud
APIs?
1. There’s no need to configure and maintain servers

97. Why should you use iCloud
APIs?
1. There’s no need to configure and maintain servers
2. Syncs across all devices without your effort

98. Why should you use iCloud
APIs?
1. There’s no need to configure and maintain servers
2. Syncs across all devices without your effort
3. Autosaving and conflict resolving

99. Why should you use iCloud
APIs?
1. There’s no need to configure and maintain servers
2. Syncs across all devices without your effort
3. Autosaving and conflict resolving
4. Easily revert to a previous version

100. iCloud

101. iCloud

102. iCloud
Document storage

103. iCloud
Document storage

104. iCloud
Document storage Key-value storage

105. Document storage
Application
sandbox

106. Document storage
Application
sandbox

107. Document storage
Application iCloud-monitored
sandbox directory

108. Document storage
Application iCloud-monitored
NSFileManager
sandbox directory

109. Document storage
Application iCloud-monitored
NSFileManager
sandbox directory

110. Document storage
setUbiquitous:YES
Application iCloud-monitored
NSFileManager
sandbox directory

111. Document storage
setUbiquitous:YES
Application iCloud-monitored
NSFileManager
sandbox directory

112. Document storage
setUbiquitous:YES
Application iCloud-monitored
NSFileManager
sandbox directory
setUbiquitous:NO

113. Limitations

114. Limitations
1. Does not work on simulator

115. Limitations
1. Does not work on simulator
2. A provisioning profile and entitlements are needed to test

116. Limitations
1. Does not work on simulator
2. A provisioning profile and entitlements are needed to test
3. All files stored in iCloud must be managed by an object that
implements NSFilePresenter protocol

117. Limitations
1. Does not work on simulator
2. A provisioning profile and entitlements are needed to test
3. All files stored in iCloud must be managed by an object that
implements NSFilePresenter protocol
UIKit provides UIDocument class which implements
NSFilePresenter protocol

118. Be responsible!

119. Be responsible!
1. Don’t store any auto generated files in iCloud.

120. Be responsible!
1. Don’t store any auto generated files in iCloud.
2. Don’t keep any copies of files tracked by iCloud.

121. Be responsible!
1. Don’t store any auto generated files in iCloud.
2. Don’t keep any copies of files tracked by iCloud.
3. Be careful with large files. Space is limited.

122. Be responsible!
1. Don’t store any auto generated files in iCloud.
2. Don’t keep any copies of files tracked by iCloud.
3. Be careful with large files. Space is limited.
4. Key-value storage has a limit of 64kb.

123. Demo

124. Where to go from here?

125. Where to go from here?

126. Where to go from here?
http://www.raywenderlich.com/934/core-data-tutorial-getting-started

127. Where to go from here?
http://www.raywenderlich.com/934/core-data-tutorial-getting-started
https://developer.apple.com/videos/wwdc/2011/

128. Where to go from here?
http://www.raywenderlich.com/934/core-data-tutorial-getting-started
https://developer.apple.com/videos/wwdc/2011/
http://developer.apple.com/library/mac/#documentation/cocoa/
Conceptual/Archiving/Archiving.html

129. Thank you!
https://github.com/Tuszy/UserDefaultsSample
https://github.com/Tuszy/NSCacheSample
https://github.com/Tuszy/ArchivesSample
https://github.com/Tuszy/CoreDataSample
https://github.com/Tuszy/iCloudSample
@srgtuszy
srgtuszy@gmail.com
srgtuszy.github.com