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