The document discusses beginning development with iCloud. It provides an overview of iCloud and how it works, outlines alternatives to iCloud like Dropbox and Parse, and dives into some technical details of implementing iCloud syncing for documents and custom data types using features like UIDocument, NSMetadataQuery, NSUbiquitousKeyValueStore, and conflict resolution. Tips are provided around testing, file handling best practices, and deciding whether to use iCloud or alternative services.

1. Beginning iCloud
development
Rocchi Cesare
@_funkyboy studiomagnolia.com

2. Outline
What is iCloud?
How does it work?
Are there alternatives?

3. Who am I?

4. UX designer and developer

5. mnml

6. < is >

7. execution matters

8. lean approach

9. 1000 details coming together

10. Giveaway

11. 1 of the Wenderlich’s
raywenderlich.com

13. ARC GameCenter API
Storyboards
News Stand
iCloud
Turn Based Gaming OpenGL ES 2.0

14. twitter.com/_funkyboy
cesare@studiomagnolia.com

15. Giveaway

16. Giveaway
(yes, another)

17. www.icloudfordevelopers.com

18. UIDocument
Key-Value store
Conflict
Resolution
CoreData
Custom
Documents
www.icloudfordevelopers.com

19. twitter.com/_funkyboy
cesare@studiomagnolia.com
www.icloudfordevelopers.com

20. Who are you?

21. What is iCloud?

22. 6028 Startown Rd, Maiden, NC

23. Stores and synchs stuff

24. It just works ...

25. ... when it works

26. Seamlessness can be a limit

27. Pros (for devs)
No server setup
No costs
No rumination on synch

28. Cons (for devs)
Stick to a synch model
No http API
No control on upload

29. Pros and Cons for users
Expectation

30. Under the hood

32. Daemon
Monitors changes
Works on metadata
Shreds files

33. Special folder, synched

34. Synched when “appropriate”

35. Appropriate
Which OS?
Which connection?
Battery status?

36. Placeholders

39. Information Structure
Document
Key-value
CoreData

40. UIDocument

41. UIDocument
NSFilePresenter
Non-blocking read/write

43. -(void) openWithCompletionHandler:^(BOOL success) { }

44. - (BOOL)loadFromContents:(id)contents
ofType:(NSString *)typeName
error:(NSError **)outError { }

45. @interface SMNote : UIDocument

46. @implementation SMNote
- (BOOL)loadFromContents:(id)contents
ofType:(NSString *)typeName
error:(NSError **)outError {
if ([contents length] > 0) {
self.myContent = [[NSString alloc]
initWithBytes:[contents bytes]
length:[contents length]
encoding:NSUTF8StringEncoding];
} else {
// Default content
self.myContent = @"Empty";
}
return YES;
}

47. - (BOOL) saveToURL:(NSURL *)url
forSaveOperation:UIDocumentSaveForOverwriting
completionHandler:^(BOOL success) { }

48. - (id)contentsForType:(NSString *)typeName
error:(NSError **)outError {}

49. - (id)contentsForType:(NSString *)typeName
error:(NSError **)outError {
return [NSData dataWithBytes:[self.myContent UTF8String]
length:[self.myContent length]];
}

50. Autosave
updateChangeCount:
use the methods of the undoManager

51. @implementation SMNote
@synthesize noteContent;
// Called whenever the application reads data
- (BOOL)loadFromContents:(id)contents
ofType:(NSString *)typeName
error:(NSError **)outError {
}
// Called whenever the application (auto)saves the content
- (id)contentsForType:(NSString *)typeName
error:(NSError **)outError {
}

52. Opening a document

53. Opening a document
Build and run a query
Wait for results
Unfold results

54. #import "SMNote.h"
@interface SMAppDelegate : UIResponder <UIApplicationDelegate>
@property (strong, nonatomic) UIWindow *window;
@property (strong, nonatomic) SMViewController *viewController;
@property (strong) SMNote *doc;
@property (strong) NSMetadataQuery *query;
- (void)loadDocument;
@end

55. NSMetadataQuery

56. - (void)loadDocument {
NSMetadataQuery *query = [[NSMetadataQuery alloc] init];
_query = query;
[query setSearchScopes:[NSArray arrayWithObject:
NSMetadataQueryUbiquitousDocumentsScope]];
}

57. - (void)loadDocument {
NSMetadataQuery *query = [[NSMetadataQuery alloc] init];
_query = query;
[query setSearchScopes:[NSArray arrayWithObject:
NSMetadataQueryUbiquitousDocumentsScope]];
NSPredicate *pred = [NSPredicate predicateWithFormat:
@"%K == %@",
NSMetadataItemFSNameKey, kFILENAME];
[query setPredicate:pred];
}

58. - (void)loadDocument {
NSMetadataQuery *query = [[NSMetadataQuery alloc] init];
_query = query;
[query setSearchScopes:[NSArray arrayWithObject:
NSMetadataQueryUbiquitousDocumentsScope]];
NSPredicate *pred = [NSPredicate predicateWithFormat:
@"%K == %@",
NSMetadataItemFSNameKey, kFILENAME];
[query setPredicate:pred];
[[NSNotificationCenter defaultCenter]
addObserver:self
selector:@selector(queryDidFinish:)
name:NSMetadataQueryDidFinishGatheringNotification
object:query];
[query startQuery];
}

59. NSPredicate *pred = [NSPredicate predicateWithFormat:
@"%K like 'Note_*'",
NSMetadataItemFSNameKey];

60. Asynchronous!

61. - (void)queryDidFinish:(NSNotification *)notification {
NSMetadataQuery *query = [notification object];
[query disableUpdates];
[query stopQuery];
[[NSNotificationCenter defaultCenter]
removeObserver:self
name:NSMetadataQueryDidFinishGatheringNotification
object:query];
_query = nil;
! [self loadData:query];
}

62. - (void)loadData:(NSMetadataQuery *)query {
if ([query resultCount] == 1) {
NSMetadataItem *item = [query resultAtIndex:0];
NSURL *url = [item valueForAttribute:NSMetadataItemURLKey];
SMNote *doc = [[SMNote alloc] initWithFileURL:url];
}
}

63. - (void)loadData:(NSMetadataQuery *)query {
if ([query resultCount] == 1) {
NSMetadataItem *item = [query resultAtIndex:0];
NSURL *url = [item valueForAttribute:NSMetadataItemURLKey];
self.doc = [[SMNote alloc] initWithFileURL:url];
[self.doc openWithCompletionHandler:^(BOOL success) {
if (success) {
NSLog(@"iCloud document opened");
} else {
NSLog(@"failed opening document from iCloud");
}
}];
}
}

64. else {
NSURL *ubiq = [[NSFileManager defaultManager]
URLForUbiquityContainerIdentifier:nil];
NSURL *ubiquitousPackage =
[[ubiq URLByAppendingPathComponent: @"Documents"]
URLByAppendingPathComponent:kFILENAME];
SMNote *doc = [[SMNote alloc]
initWithFileURL:ubiquitousPackage];
}

65. else {
NSURL *ubiq = [[NSFileManager defaultManager]
URLForUbiquityContainerIdentifier:nil];
NSURL *ubiquitousPackage =
[[ubiq URLByAppendingPathComponent: @"Documents"]
URLByAppendingPathComponent:kFILENAME];
SMNote *doc = [[SMNote alloc]
initWithFileURL:ubiquitousPackage];
self.doc = doc;
[doc saveToURL: [doc fileURL]
forSaveOperation:UIDocumentSaveForCreating
completionHandler:^(BOOL success) {
if (success) {
[doc openWithCompletionHandler:^(BOOL success) {
NSLog(@"new document opened from iCloud");
}];
}
}];
}

66. - (BOOL)application:(UIApplication *)application
didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
...
[self.window makeKeyAndVisible];
NSURL *ubiq = [[NSFileManager defaultManager]
URLForUbiquityContainerIdentifier:nil];
if (ubiq) {
NSLog(@"iCloud access at %@", ubiq);
[self loadDocument];
} else {
NSLog(@"No iCloud access");
}
return YES;
}

67. - (BOOL)application:(UIApplication *)application
didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
...
[self.window makeKeyAndVisible];
NSURL *ubiq = [[NSFileManager defaultManager]
URLForUbiquityContainerIdentifier:nil];
if (ubiq) {
NSLog(@"iCloud access at %@", ubiq);
[self loadDocument];
} else {
NSLog(@"No iCloud access");
}
return YES;
}

68. - (void)viewDidLoad {
[super viewDidLoad];
[[NSNotificationCenter defaultCenter]
addObserver:self
selector:@selector(dataReloaded:)
name:@"noteModified"
object:nil];
}
- (void)dataReloaded:(NSNotification *)notification {
self.doc = notification.object;
self.noteView.text = self.doc.noteContent;
}

69. Switching on/off

70. - (NSURL *) localNotesURL {
return [[[NSFileManager defaultManager]
URLsForDirectory:NSDocumentDirectory
inDomains:NSUserDomainMask] lastObject];
}
- (NSURL *) ubiquitousNotesURL {
return [[[NSFileManager defaultManager]
URLForUbiquityContainerIdentifier:nil]
URLByAppendingPathComponent:@"Documents"];
}

71. - (void) setNoteUbiquity {
NSURL *baseUrl = [self localNotesURL];
if (_useiCloud)
baseUrl = [self ubiquitousNotesURL];
NSURL *destUrl = [baseUrl URLByAppendingPathComponent:
[note.fileURL lastPathComponent]];
[[NSFileManager defaultManager] setUbiquitous:_useiCloud
itemAtURL:note.fileURL
destinationURL:destUrl
error:NULL];
}
Don’t call it on the main thread!

72. - (void) startMigration {
NSOperationQueue *iCloudQueue = [NSOperationQueue new];
NSInvocationOperation *op =
[[NSInvocationOperation alloc]
initWithTarget:self
selector:@selector(setNoteUbiquity)
object:nil];
[iCloudQueue addOperation:op];
}

73. Custom documents

74. SMNotesDocument
SMNote SMNote SMNote
...

75. @interface SMNote : NSObject <NSCoding>
@property (copy, nonatomic) NSString *noteId;
@property (copy, nonatomic) NSString *noteContent;
@property (strong, nonatomic) NSDate *createdAt;
@property (strong, nonatomic) NSDate *updatedAt;
@end

76. #import "SMNote.h"
@interface SMNotesDocument : UIDocument
@property (nonatomic, strong) NSMutableArray *entries;
@property (nonatomic, strong) NSFileWrapper *fileWrapper;
@end

77. #import "SMNote.h"
@interface SMNotesDocument : UIDocument
@property (nonatomic, strong) NSMutableArray *entries;
@property (nonatomic, strong) NSFileWrapper *fileWrapper;
@end

78. - (id)contentsForType:(NSString *)typeName
error:(NSError **)outError {
NSMutableDictionary *w = [NSMutableDictionary dictionary];
NSMutableData *data = [NSMutableData data];
NSKeyedArchiver *arch = [[NSKeyedArchiver alloc]
initForWritingWithMutableData:data];
[arch encodeObject:_entries forKey:@"entries"];
[arch finishEncoding];
}

79. - (id)contentsForType:(NSString *)typeName
error:(NSError **)outError {
NSMutableDictionary *w = [NSMutableDictionary dictionary];
NSMutableData *data = [NSMutableData data];
NSKeyedArchiver *arch = [[NSKeyedArchiver alloc]
initForWritingWithMutableData:data];
[arch encodeObject:_entries forKey:@"entries"];
[arch finishEncoding];
NSFileWrapper *entriesWrapper = [[NSFileWrapper alloc]
initRegularFileWithContents:data];
[w setObject:entriesWrapper forKey:@"notes.dat"];
// add other wrappers if you like
NSFileWrapper *res = [[NSFileWrapper alloc]
initDirectoryWithFileWrappers:w];
return res;
}

80. - (BOOL)loadFromContents:(id)contents
ofType:(NSString *)typeName
error:(NSError **)outError {
NSFileWrapper *wrapper = (NSFileWrapper *)contents;
NSDictionary *d = [wrapper fileWrappers];
NSFileWrapper *entriesWrap = [d objectForKey:@"notes.dat"];
}

81. - (BOOL)loadFromContents:(id)contents
ofType:(NSString *)typeName
error:(NSError **)outError {
NSFileWrapper *wrapper = (NSFileWrapper *)contents;
NSDictionary *d = [wrapper fileWrappers];
NSFileWrapper *entriesWrap = [d objectForKey:@"notes.dat"];
NSData *data = [entriesWrap regularFileContents];
NSKeyedUnarchiver *arch = [[NSKeyedUnarchiver alloc]
initForReadingWithData:data];
_entries = [arch decodeObjectForKey:@"entries"];
// Notify the view
}

82. Uniform Type Identifier

84. Key-value

85. Key-value
1Mb

86. Key-value
1Mb
was 64Kb !

87. - (void) saveNoteAsCurrent {
[[NSUbiquitousKeyValueStore defaultStore]
setString:self.currentNote.noteId
forKey:@"com.studiomagnolia.currentNote"];
[[NSUbiquitousKeyValueStore defaultStore] synchronize];
}

88. - (void) saveNoteAsCurrent {
[[NSUbiquitousKeyValueStore defaultStore]
setString:self.currentNote.noteId
forKey:@"com.studiomagnolia.currentNote"];
[[NSUbiquitousKeyValueStore defaultStore] synchronize];
}
NSString *currentNoteId =
[[NSUbiquitousKeyValueStore defaultStore] stringForKey:
@"com.studiomagnolia.currentNote"];

89. NSUbiquitousKeyValueStore* store =
[NSUbiquitousKeyValueStore defaultStore];
[[NSNotificationCenter defaultCenter]
addObserver:self
selector:@selector(updateCurrentNoteIfNeeded:)
name:NSUbiquitousKeyValueStoreDidChangeExternallyNotification
object:store];
[store synchronize];

90. Conflict Resolution

91. Conflict Resolution
Up to the dev
documentState

92. DocumentStates
UIDocumentStateNormal
UIDocumentStateClosed
UIDocumentStateInConflict
UIDocumentStateSavingError
UIDocumentStateEditingDisabled

93. UIDocumentStateChangedNotification

94. [[NSNotificationCenter defaultCenter]
addObserver:self
selector:@selector(noteHasChanged:)
name:UIDocumentStateChangedNotification
object:nil];

95. UIDocumentState s = [n documentState];
switch (s) {
case UIDocumentStateNormal:
NSLog(@"Everything is fine");
break;
case UIDocumentStateInConflict:
NSLog(@"There is a conflict");
break;
...
default:
NSLog(@"Unknown state");
break;
}

96. UI conflict
vs
iCloud conflict

97. Resolution policy
last wins
prompt user
automatic merge

98. Resolution policy
last wins
prompt user
automatic merge
NSFileVersion

99. NSError *err;
NSURL *url = [[NSFileManager defaultManager]
URLForPublishingUbiquitousItemAtURL:[self.currentNote fileURL]
expirationDate:&expirationInOneHourSinceNow
error:&err];

101. Tips & Tricks

102. Patience!

103. Test on wireless & 3G

104. Regenerate provisioning

105. Delete previous data

107. Restart device

108. API throttle!

109. App policy
Be gentle with storage
<App_home>/tmp
<App_home>/Library/Caches/

110. App policy
Documents is backed up
mark files as “do not backup”

111. // iOS 5.0.1
#import <sys/xattr.h>
- (BOOL)addSkipBackupAttributeToItemAtURL:(NSURL *)URL {
const char* filePath = [[URL path] fileSystemRepresentation];
const char* attrName = "com.apple.MobileBackup";
u_int8_t attrValue = 1;
int result = setxattr(filePath, attrName, &attrValue,
sizeof(attrValue), 0, 0);
return result == 0;
}

112. // iOS 5.1
- (BOOL)addSkipBackupAttributeToItemAtURL:(NSURL *)URL {
NSError *error = nil;
BOOL success = [URL setResourceValue: [NSNumber numberWithBool:YES]
forKey: NSURLIsExcludedFromBackupKey
error: &error];
if(!success){
NSLog(@"Error excluding %@ from backup %@",
[URL lastPathComponent],
error);
}
return success;
}

113. “To iCloud or not to iCloud?”

114. Alternatives

115. Alternatives
dropbox
parse.com
cloudmine
stackmob
custom

116. Dropbox
documents
authentication
no notifications

117. Dropbox
other platforms
no CR (revision #)
expectation

118. Parse

119. Parse
ORM approach
Recently released
No cost of infrastructure

120. Parse
Pay as you use
Limit of calls/mo

121. PFObject *note = [PFObject objectWithClassName:@"Note"];
[note setObject:@"Ciao"
forKey:@"title"];
[note setObject:@"Note on Parse"
forKey:@"content"];
[note save];
//[note saveInBackground];
//[note saveEventually];

122. [note saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error)
{
if (error) {
NSLog(@"Note not saved");
} else {
NSLog(@"Note saved successfully");
}
}];

123. Parse
Other platforms
REST API
Push notifications
Object browser

124. curl -X POST
-H "X-Parse-Application-Id: ${APPLICATION_ID}"
-H "X-Parse-REST-API-Key: ${REST_API_KEY}"
-H "Content-Type: application/json"
-d '{"note": 001,
"title": "Ciao",
"content": “Note on parse” }'
https://api.parse.com/1/classes/GameScore

125. PFObject *note = [PFObject objectWithClassName:@"Note"];
[note setObject:@"Ciao"
forKey:@"title"];
[note setObject:@"Note on parse"
forKey:@"content"];
PFObject *myTag = [PFObject objectWithClassName:@"Tag"];
[myTag setObject:@"important"
forKey:@"tagName"];
// Add a relation
[note setObject:myTag forKey:@"tag"];
// Saves both
[note saveInBackground];

126. Recap
UIDocument
Key-Value store
Alternatives

127. “You can’t always get what
you want
but if you try sometime, you
just might find ...”

128. “You can’t always get what
you want
but if you try sometime, you
just might find ...”
Rolling Stones

129. Contact
twitter.com/_funkyboy
cesare@studiomagnolia.com
http://studiomagnolia.com