Slides for a presentation on iOS that I gave at the fall 2012 Near Infinity conference. Links to the sample applications on GitHub are in the slides.

1. iOS
Scott
Leberknight

2. The Big Picture
Patterns
Languages
APIs
Tools

3. Patterns
MVC(S)
Delegation
Protocols
Notifications
Target-Action

4. Languages
Objective-C
C
(lower-level APIs)

5. APIs
Core
UIKit Foundation Core Graphics
Lots more...
MapKit Core Location OpenGL
Core Data GameKit Social Accounts
...

6. Tools XCode

7. Tools Interface Builder

8. First App*
Delegation
MVC
Target-Action
* http://github.com/sleberknight/fortune-ios-app

9. Model
@property (nonatomic, copy) NSArray *fortunes;
FOViewController.h

10. View
Outlets
&
Actions
FOViewController.xib

11. Outlets
in XCode...
FOViewController.h

12. Outlets in IB...
FOViewController.xib

13. Target-Action
Target - File’s Owner
Action - “touch up inside”
(our view controller)

14. Controller
#import <UIKit/UIKit.h>
@interface FOViewController : UIViewController
// Model
@property (nonatomic, copy) NSArray *fortunes;
// Outlets
@property (nonatomic, strong) IBOutlet UITextView *fortuneField;
// Actions
- (IBAction)showFortune:(id)sender;
@end
words allow
(IBOutlet & IBAction key
ilder)
connections in Interface Bu
FOViewController.h

15. Controller
#import "FOViewController.h"
@implementation FOViewController
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
_fortunes = @[
@"A dubious friend may be an enemy in camouflage.",
@"A feather in the hand is better than a bird in the air.",
@"A friend asks only for your time not your money.",
// ...
];
}
return self;
}
- (IBAction)showFortune:(id)sender {
int fortuneIndex = arc4random() % [_fortunes count];
NSLog(@"fortuneIndex: %d", fortuneIndex);
NSString *fortune = [_fortunes objectAtIndex:fortuneIndex];
[_fortuneField setText:fortune];
}
@end
FOViewController.m

16. Delegation
#import <UIKit/UIKit.h>
// Inherits from UIResponder
// Conforms to UIApplicationDelegate protocol
@interface FOAppDelegate : UIResponder <UIApplicationDelegate>
@property (strong, nonatomic) UIWindow *window;
@end
FOAppDelegate.h

17. Delegation
#import "FOAppDelegate.h"
#import "FOViewController.h"
@implementation FOAppDelegate
- (BOOL)application:(UIApplication *)application
didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
// Create our view controller; set it as the root view controller
FOViewController *viewController = [[FOViewController alloc]
initWithNibName:@"FOViewController"
bundle:nil];
[[self window] setRootViewController:viewController];
self.window.backgroundColor = [UIColor whiteColor];
[self.window makeKeyAndVisible];
return YES;
}
@end
FOAppDelegate.m

18. Run It!
1. Load view controller
in App Delegate
2. Tap “Get Fortune!”
3. showFortune: called
4. Get fortune from model
5. Call setText: on UITextView

19. Objective-C
Object-oriented
(layered on top of C)
Single-inheritance
Protocols (like Java interfaces)
Message sending

20. Objective-C (continued)
Properties
Blocks (like closures)
Selectors
ARC (automatic reference counting)
GCD (Grand Central Dispatch)

21. Properties
@property (nonatomic, strong) IBOutlet UITextView *fortuneField;
* Modifiers determine threading and storage model
* IBOutlet indicates it can be an outlet to IB
* Compiler generates:
- instance variable _fortuneField
- getter method fortuneField
- setter method setFortuneField

22. Sending Messages
selector
[detailViewController setItem:newItem];
receiver argument

23. Sending Messages
receiver
[self presentViewController:navigationController
animated:YES
completion:nil];
selector arguments

24. Creating Objects
WLItemsViewController *itemsViewController =
[[WLItemsViewController alloc] init];
initialize
allocate object
memory

25. Blocks
int amountToAdd = 7;
int (^adder)(int) = ^(int num) {
return num + amountToAdd;
};
NSLog(@"%d", adder(3));
// prints "10" to XCode console

26. Blocks - inline
[detailViewController setDismissBlock:^{
[[self tableView] reloadData];
}];
[self tableView] is captured
from scope defining block!

27. Objective-C really is an OK language,
once you get used to its quirks,
and it keeps improving...

28. Core APIs
UIKit
Foundation
Core Graphics

29. UIKit
“The UIKit framework provides the classes needed to
construct and manage an application’s user interface for iOS.
It provides an application object, event handling, drawing model,
windows, views, and controls specifically designed for a touch
screen interface.”
http://developer.apple.com/library/ios/#documentation/uikit/reference/UIKit_Framework/_index.html

30. UIKit & Grand Central Dispatch
"For the most part, UIKit classes should be used only from an
application’s main thread. This is particularly true for classes
derived from UIResponder or that involve manipulating your
application’s user interface in any way."
http://developer.apple.com/library/ios/#documentation/uikit/reference/UIKit_Framework/
Introduction/Introduction.html#//apple_ref/doc/uid/TP40006955-CH1-SW1

31. Update UI using GCD
-(void)handleIncoming:(NSData *)data
{
dispatch_async(dispatch_get_main_queue(), ^{
// Retrieve data...
// Update the UI using UIKit methods...
});
}

32. Foundation
“The Foundation framework defines a base layer of
Objective-C classes. In addition to providing a set of useful
primitive object classes, it introduces several paradigms that
define functionality not covered by the Objective-C language.”
http://developer.apple.com/library/mac/#documentation/cocoa/reference/foundation/ObjC_classic/_index.html

33. Core Graphics
“The Core Graphics framework is a C-based API that is
based on the Quartz advanced drawing engine. It provides low-
level, lightweight 2D rendering with unmatched output fidelity.
You use this framework to handle path-based drawing,
transformations, color management, offscreen rendering,
patterns, gradients and shadings, image data management,
image creation, masking, and PDF document creation, display,
and parsing.”
http://developer.apple.com/library/ios/#documentation/coregraphics/reference/coregraphics_framework/_index.html

34. Many, Many More APIs
Core Location MapKit
Quartz Core Animation
Core Motion AdSupport...

35. Sample Application - Wishlist *
Displays list of items
Move and delete items in list
Detail view to create/edit items
Choose images for items
* http://github.com/sleberknight/wishlist-ios-app

36. List of items Editing list

37. Add/edit
item
Choose
image

38. Patterns
MVC(S):
Model, View, Controller (, Store)
“Store” is like a DAO (data access object)
Extract store logic from controllers

39. Patterns
Inheritance - e.g. table view controller
Delegation - e.g. image picker delegate
Notification - e.g. low-memory warning

40. Model - WLItem
#import <Foundation/Foundation.h>
@interface WLItem : NSObject <NSCoding>
-(id)initWithItemName:(NSString *)name;
-(id)initWithItemName:(NSString *)name
occasion:(NSString *)occasion
store:(NSString *)store
price:(int)price;
@property (nonatomic, strong) WLItem *containedItem;
@property (nonatomic, weak) WLItem *container;
@property (nonatomic, copy) NSString *itemName;
@property (nonatomic, copy) NSString *occasion;
@property (nonatomic, copy) NSString *store;
@property (nonatomic, assign) int price;
@property (nonatomic, copy) NSString *imageKey;
@property (readonly, nonatomic, copy) NSDate *dateCreated;
@property (nonatomic, copy) NSDate *dateModified;
@end

41. Views
UITableView (presents list of items)
* Not defined in XIB
* App delegate creates table view
controller programmatically within
a navigation controller
* Edit and + buttons defined in code

42. Views Detail View Controller

43. Controllers
WLItemsViewController:
Subclass of: UITableViewController
Conforms to: UITableViewDelegate
UITableViewDataSource
Responsible for creating table view cells
Manages moving/deleting items
Uses UINavigationController to
present detail view controller for
adding/editing items

44. Controllers
WLDetailViewController:
Subclass of: UIViewController
Conforms to: UITextFieldDelegate
UINavigationControllerDelegate
UIImagePickerControllerDelegate
UIPopoverControllerDelegate
Responsible for loading/saving items & images
Manages image picking controllers
Manages text changed notifications

45. Stores
WLItemStore
Stores WLItem objects
WLImageStore
Stores UIImage objects

46. Application Flow

47. WLAppDelegate
application:didFinishLaunchingWithOptions
- Create a WLItemsViewController
- Create a UINavigationController
- Embed WLItemsViewController in
UINavigationController
WLItemsViewController
viewWillAppear: loads table view
List editing UI is automatic when
add button using editBarButton
Tap + button, fires addNewItem: which
presents detail view controller

48. WLDetailViewController init: creates
Cancel & Done bar button items
viewDidLoad: sets background color
viewWillAppear:animated:
- Sets up form for editing/adding item
- Display image if present
- Register for text change notifications
done: dismisses controller,
completion handler reloads table data
viewWillDisappear: saves item data

49. Tapping camera button
invokes takePicture:
UIImagePickerController
presents camera or picture
library
UIImagePickerController
delegate (controller) handles
selected image

50. imagePickerController:
didFinishPickingMediaWithInfo
retrieves selected image, stores it,
and displays it
Use Core Graphics to add a border
around image
Use Quartz to add a shadow around
image

51. UITextFieldDelegate method
textFieldShouldReturn:
dismisses keyboard when
return tapped
UIControlEventEditingChanged
events trigger selector
textChanged: which adds
modified date when editing
existing items

52. On iPad use a UIPopoverController for selecting images

53. UIPopoverController was used to select the delicious image...

54. One more thing...

55. Storyboards (an alternative way to define app flow)

56. Summary
Patterns, Languages, APIs, Tools
MVC(S), Delegation, Protocols
Objective-C
Lots of APIs to use (and learn)
XCode / Interface Builder (IB)
Connect outlets & actions in IB

57. References
http://pragprog.com/book/adios/ios-sdk-development
http://www.bignerdranch.com/book/ios_programming_the_big_nerd_ranch_guide_rd_edition_

58. Sample Code
Fortunes:
http://github.com/sleberknight/fortune-ios-app
Wishlist:
http://github.com/sleberknight/wishlist-ios-app
Fortunes:

59. My Info
scott.leberknight at nearinfinity.com
twitter.com/sleberknight
www.sleberknight.com/blog
www.nearinfinity.com/blogs/scott_leberknight/all/