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First Steps in iOS Development

Sasha Goldshtein

CTO, Sela Group

@goldshtn blog.sashag.net

Join the conversation on Twitter: @SoftArchConf #SoftArchConf

The iOS Platform


Platform Philosophy


iOS Devices and VersionsSeptember 2013:

≈95% of iOS devices run iOS 6


Devices and Resolutions

Don’t worry about Retina: all you need to do is provide 2x images for your graphical assets

Don’t worry about iPhone 5: most views will resize correctly with AutoLayout or require minimal tweaks


Developing for iOS

self.title = [NSString initWithFormat:@"%d", n];[button setTitle:self.title forState:UIControlStateNormal];


Objective C Classes

• Declare in .h file, implement in .m file– @interface and @implementation keywords


Methods

@interface Cat : NSObject- (void)meow;- (BOOL)doesLikeOtherCat:(Cat *)other;- (int)age;@end

@implementation Cat- (void)meow { NSLog(@"Meow"); }- (int)age { return 7; }- (BOOL)doesLikeOtherCat:(Cat *)other { if ([self age] <= [other age]) return YES; return NO;}@end

Q: What about nil checks?!A: Messages sent to nil return 0/nil/NO


Initializers

@interface Cat : Mammal { int age_; // This is a public instance field}- (id)initWithAge:(int)age;@end

@implementation Cat- (id)initWithAge:(int)age { self = [super init]; if (self) age_ = age; return self;}@end


Properties

@interface Cat : NSObject@property (nonatomic) int age;- (id)initWithAge:(int)age;@end

@implementation Cat

- (id)initWithAge:(int)age { if (self = [super init]) _age = age; // Auto-generated field! return self;}

@end


Using Objects

Cat *felix = [[Cat alloc] initWithAge:5];Cat *shadow = [[Cat alloc] initWithAge:4];

if ([felix likesOtherCat:shadow]) { // Left to your imagination}

NSDate *today = [NSDate date]; // Current dateif ([Calendar isBirthday:shadow onDate:today]) { shadow.age++; [shadow meow];}


Memory Management: ARC

• Heap objects are reference counted– Support release, retain, retainCount

messages

• Automatic Reference Counting (ARC) takes care of memory management– The compiler embeds the appropriate

reference counting messages automatically– Introduced in iOS 4 with LLVM compiler– With one caveat: reference cycles


Basic Foundation Classes

• Strings– Immutable/mutable, @"foo" syntax

• Arrays– May contain any object type (NSObject)– Immutable/mutable, @[a, b, c] syntax

• Dictionaries– Keys are usually strings, but don’t have to be– Immutable/mutable, @{ a : b } syntax


DEMOOur first iOS app


Project Components• Generated files:

– Application delegate– Initial view controller– Main storyboard– Property list– File for localizable strings– Application icons

• Xcode also adds basic frameworks to your app


iOS MVC Fundamentals


Outlets and Actions

• Xcode connects views and controllers– Controller manipulates views through outlets– Controller receives events through actions

@interface MyViewController : UIViewController

@property (nonatomic, weak) IBOutlet UITextField *petName;- (IBAction)getQuote;

@end


DEMOConnecting UI to code


iOS Navigation Types

• Tab bar controller

• Navigation controller


Storyboards

• The storyboard describes your application’s view controllers and connects them with segues


Types of Segues


Passing Parameters

• Usually the source view controller sets properties or calls methods on the destination view controller

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{ MySecondVC *vc = segue.destinationViewController; vc.itemToDisplay = [self selectedItem]; vc.delegate = self; // For callbacks}


DEMOStoryboards and segues


Summary

• It’s just another{language, IDE, UI framework}

• The rest is just details: data, networking, settings, table views, styling, …

Thank You!

Sasha Goldshtein

CTO, Sela Group

@goldshtn blog.sashag.net