This document outlines an iOS development lecture on practical iOS development topics including using maps and location services, system dialogs for contacts, photos, email and SMS, social networks APIs, threading with NSThread, GCD and NSOperation, and best practices for singletons. Key classes and methods are described for adding maps, determining user location, geocoding, contacts pickers, photo pickers, mail/SMS composers, Twitter and Facebook SDKs, threads, operations, and thread-safe singletons.

1. iOS Development
Lecture 2 - The practical stuff
Petr Dvořák
Partner & iOS Development Lead
@joshis_tweets

2. Outline

3. Outline
• Using location services and maps
• Adding maps to an app
• Determining user’s location
• Geocoding/Reverse geocoding

4. Outline
• Using system dialogs
• Picking a contact
• Taking a photo
• Composing an e-mail or SMS

5. Outline
• Getting a bit social
• Twitter API
• Facebook iOS SDK

6. Outline
• Threading
• NSThread
• GCD (Grand Central Dispatch)
• NSOperation

7. Outline
• If there is still time...
• Using UIWebView
• iOS app localization

8. Maps & Location

9. MapKit
• Implementation of
Google Maps
• High-level API
• Annotations, Routes,
Overlays

10. MKMapView
• UIView subclass
• Based on adding “annotations”
• = model classes
• Support for user’s location
• Customizable maps & annotations
• Delegate-based API

11. MKAnnotation
• Protocol that enables model class for
showing up on maps
• coordinate, title, subtitle
• MKPlacemark
• conforms to MKAnnotation
• country, state, city, address

12. MKAnnotationView
• View related to a particular
MKAnnotation instance
• Reused in the map view
• MKPinAnnotationView
• The classic “iOS map pin”
• Three colors

13. Core Location
• Access to GPS module
• Configurable precision (vs. time)
• Significant Location Changes
• May run on background

14. CLLocationManager
• Provides callbacks for location and
heading
• Delegate based
• Check for availability and state of the
location services before using

15. CLGeocoder
• Allows geocoding and reverse
geocoding
• Does not use Google API
• ... doesn’t work perfectly outside the USA
• Block based

16. CLGeocoder* g = [[CLGeocoder alloc] init];
[g reverseGeocodeLocation:location
completionHandler:^(NSArray *placemark, NSError *error) {
// ...
}];
[g geocodeAddressString:@”Brno”
completionHandler: ^(NSArray *placemark, NSError *error) {
// ...
}];
// [g cancelGeocode];

17. System dialogs

18. System dialogs
• Allow performing usual tasks in
a consistent manner
• Complete process handling
• Delegate based

19. Address Book
• Creating and searching contacts
• Allows manual access via C API
• ABAddressBookCreate
• ABAddressBookCopyArrayOfAllPeople
• ABAddressBookSave
• Contains predefined dialogs

20. ABPeoplePickerNavigationController
• System dialog for picking a contact
• Allows picking a contact or a contact
property

21. ABPeoplePickerNavigationController *pp =
[[ABPeoplePickerNavigationController alloc] init];
pp.peoplePickerDelegate = self;
[self presentModalViewController:pp
animated:YES];
//...
- (BOOL)peoplePickerNavigationController:(ABPeoplePickerNavigationController*)p
shouldContinueAfterSelectingPerson:(ABRecordRef)person
property:(ABPropertyID)property
identifier:(ABMultiValueIdentifier)identifier
{
//...
}

22. ABNewPersonViewController
• System dialog for creating a contact
• May be pre-initialized
ABPersonViewController
• System dialog for displaying a contact
• Optional editing

23. UIImagePickerController
• System dialog for picking a photo
• Uses “sourceType” flag to determine
source
• camera, library, saved photos
• Check for camera before touching it
• Delegate based

24. MFMailComposeViewController
• System dialog for composing an
e-mail message
• May be pre-filled with e-mail data
• Support for attachments
• + (BOOL) canSendMail;

25. MFMessageComposeViewController
• System dialog for composing an
SMS message
• No MMS / attachments
• May be pre-filled with message body
and recipients (string array)
• + (BOOL) canSendText;

26. Social Networks

27. Twitter API
• Native Twitter support
since iOS 5
• Uses Twitter app for
authentication
• Twitter uses OAuth 1.0a
under the hood =>
secure, hard to
implement

28. TWTweetComposeViewController
• System dialog for composing an
Tweet
• Text, Images, URLs
• add methods return NO if length exceeds 140 chars
• Block based
• TWTweetComposeViewControllerCompletionHandler
• + (BOOL) canSendTweet;

29. Facebook iOS SDK
• Facebook publishes official iOS SDK
• https://github.com/facebook/facebook-ios-sdk
• Requires Facebook application (web)
• Uses official Facebook app for
authentication
• Alternatively: web authentication, embedded FB authentication dialog
• Uses URL scheme handling

30. Threading

31. Why threads?
• Slow operations must not block UI
• Network operations
• Computations
• Filesystem operations

32. NSThread
• Low level thread abstraction
• Requires you to do all the
synchronisation manually

33. - (void) detachAsyncOperation {
[NSThread detachNewThreadSelector:@selector(operation:)
toTarget:self
withObject:contextData];
}
- (void) operation:(id)contextData {
@autorelease {
// slow code here
// ...
[self performSelectorOnMainThread:@selector(updateUI:)
withObject:contextData
waitUntilDone:NO];
}
}

34. GCD
• Working with NSThread is difficult
• GCD makes an abstraction above
threads
• C API, functions/macros starting with
“dispatch_” prefix

35. Dispatch Queue
• Queue of blocks to be performed
• FIFO, synchronized
• Reference-counted
• dispatch_queue_create ➞ dispatch_release
• One queue per use-case

36. dispatch_queue_t main_queue = dispatch_get_main_queue()
dispatch_queue_t network_queue = dispatch_get_global_queue(priority, 0);
// dispatch_queue_t network_queue2 =
// dispatch_queue_create("eu.inmite.net", NULL);
dispatch_async(network_queue, ^ {
// some slow code
dispatch_async(main_queue, ^{
// update UI
});
// dispatch_release(network_queue2);
});

37. Dispatch Semaphore
• dispatch_semaphore_create
• dispatch_semaphore_wait
• dispatch_semaphore_signal

38. NSOperation
• Abstraction above “operation”
• Meant to be subclassed
• main - code to be executed
• start - start the operation
• cancel - set the cancel flag
• Operation priority
• Dependencies
• [op1 addDependency:op2];

39. NSInvocationOperation
• NSOperation subclass
• Operation based on target & selector
[[NSInvocationOperation alloc] initWithTarget:target
selector:selector
object:context];

40. NSBlockOperation
• NSOperation subclass
• Operation based on block
[NSBlockOperation blockOperationWithBlock:^{
// some code...
}];

41. NSOperationQueue
• NSOperations are not meant to be
run directly
• NSOperationQueue runs the
operations correctly
• Configurable number of concurrent
operations

42. NSOperationQueue
NSOperationQueue *queue = [NSOperationQueue mainQueue];
// queue = [NSOperationQueue currentQueue];
// queue = [[NSOperationQueue alloc] init];
[queue addOperation:anOperation];

43. Singleton pattern
• Assures access to a shared instance
• Usually allows multiple instance
creation
• Simple pattern, many problems
• Threading

44. // within class Foo
+ (Foo*) getDefault {
static Foo *inst = nil;
if (!inst) {
inst = [[Foo alloc] init];
}
return inst;
}

45. // within class Foo
+ (Foo*) getDefault {
static Foo *inst = nil;
@synchronized (self) {
if (!inst) {
inst = [[Foo alloc] init];
}
}
return inst;
}

46. // within class Foo
+ (Foo*) getDefault {
static Foo *inst = nil;
if (!inst) { // double-check locking
@synchronized (self) {
if (!inst) {
inst = [[Foo alloc] init];
}
}
}
return inst;
}

47. // within class Foo
+ (Foo*) getDefault {
static volatile Foo *inst = nil;
if (!inst) { // double-check locking
@synchronized (self) {
if (!inst) {
Foo *tmp = [[Foo alloc] init];
OSMemoryBarrier();
inst = tmp;
}
}
}
OSMemoryBarrier();
return inst;
}

48. // within class Foo
+ (Foo*) getDefault {
static volatile Foo *inst;
static dispatch_once_t pred;
dispatch_once(&pred, ^ {
inst = [[Foo alloc] init];
});
return inst;
}

49. Thank you
http://www.inmite.eu/talks
Petr Dvořák
Partner & iOS Development Lead
@joshis_tweets