Objective-C for Rubyists

Objective-C might look like a crazy, complex and verbose language to the seasoned Rubyist. In reality, they share many features. This allows you to use your knowledge of Ruby to quickly get started with Objective-C. In this talk, I give an overview of the syntax and semantics of Objective-C and compare and contrast it with Ruby where appropriate.

Transcript

1. Objective-C for Rubyists
2. Mikael Konutgan iOS Developer, aaa – all about apps GmbH !2
3. Why Objective-C?
4. !4
5. !5
6. A Quick Example
7. Ruby numbers = [42, 14, 73] ! numbers.each_with_index do |number, idx| puts "#{idx} -> #{number}" end
8. Objective-C NSNumber *a = [NSNumber numberWithInteger:42]; NSNumber *b = [NSNumber numberWithInteger:14]; NSNumber *c = [NSNumber numberWithInteger:73]; NSArray *numbers = [[NSArray alloc] initWithObjects:a, b, c, nil]; ! for (NSUInteger index = 0; index < [numbers count]; index++) { NSLog(@"%lu -> %@", index, [numbers objectAtIndex:index]); } ! [numbers release];
9. Modern Objective-C NSArray *numbers = @[@42, @14, @73]; ! [numbers enumerateObjectsUsingBlock:^(NSNumber *number, NSUInteger idx, BOOL *stop) { NSLog(@"%lu -> %@", idx, number); }];
10. Objective-C
11. • A strict superset of C • Object oriented, but everything is NOT an object • A dynamic runtime • Static or dynamic typing for objects !11 Objective-C
12. Modern Objective-C • Object literals for arrays, hashes, numbers! • Automatic memory management!! • Enumeration with blocks!!! • Domain specific languages!!!! !12
13. A strict superset of C Everything that works in C, works in Objective-C • Control flow: if, while, for • Primitive types, int, long, char, void *, const char * • The C standard library • UNIX system calls !13
14. int n = 5; const char *str = "hello, world\n"; unsigned long len = strlen(str); ! if (len > 0) { int i = 0; while (i < n) { printf("%s", str); i++; } } C
15. Booleans BOOL shouldBeginEditing = YES; ! BOOL shouldEndEditing = NO; !15
16. Defining Classes !16
17. # user.rb ! class User end !17 Ruby
18. // KMUser.h ! @interface KMUser : NSObject ! @end !18 Objective-C
19. // KMUser.m ! @implementation KMUser ! @end !19 Objective-C
20. class User attr_accessor :name, :last_name end !20 Ruby
21. // KMUser.h ! @interface KMUser : NSObject ! @property (copy, nonatomic) NSString *name; @property (copy, nonatomic) NSString *lastName; ! @end !21 Objective-C
22. // KMUser.m ! @implementation KMUser ! @end !22 Objective-C
23. // KMUser.m ! @implementation KMUser ! @synthesize name = _name; @synthesize lastName = _lastName; ! @end !23 Objective-C
24. Ruby class User attr_accessor :name, :last_name ! def initialize(name, last_name) @name = name @last_name = last_name end end
25. // KMUser.h ! @interface KMUser : NSObject ! @property (copy, nonatomic) NSString *name; @property (copy, nonatomic) NSString *lastName; ! - (KMUser *)initWithName:(NSString *)name lastName:(NSString *)lastName; ! @end !25 Objective-C
26. // KMUser.m ! @implementation KMUser ! - (id)initWithName:(NSString *)name lastName:(NSString *)lastName { self = [super init]; if (self) { _name = name; _lastName = lastName; } return self; } ! @end !26 Objective-C
27. The Muffin Man @interface TheMuffinMan : NSObject ! - (BOOL)doYouKnowTheMuffenMan:(TheMuffinMan *)theMuffinMan; ! @end ! @implementation TheMuffinMan ! - (BOOL)doYouKnowTheMuffenMan:(TheMuffinMan *)theMuffinMan { return YES; } ! @end
28. Using classes
29. user = User.new("Mikael", "Konutgan") ! name = user.name last_name = user.last_name ! user.name = “Kristofer" user.last_name = nil !29 Ruby
30. KMUser *user = [[KMUser alloc] initWithName:@“Mikael" lastName:@“Konutgan"]; ! NSString *name = user.name; NSString *lastName = user.lastName; ! user.name = @"Kristofer"; user.lastName = nil; ! name = [user name]; lastName = [user lastName]; ! [user setName:@“Kristofer"]; [user setName:nil]; !30 Objective-C
31. Objective-C Messages
32. • initWithName:lastName: ! • replaceObjectsInRange:withObjectsFromArray:range: !32 Selectors
33. Selectors - (KMUser *)initWithName:(NSString *)name lastName:(NSString *)lastName;
34. Ruby person.say_hello("Lukas")
35. Objective-C [person sayHello:@"Lukas"];
36. Dynamic message sending
37. Ruby person.send(:say_hello, "Lukas", "French")
38. Objective-C [person performSelector:@selector(sayHello:inLanguage:) withObject:@"Lukas" withObject:@"French"];
39. SEL selector = NSSelectorFromString(@"sayHello:inLanguage:"); Objective-C !39
40. Objects
41. Objective-C • Objects are all pointers • But you (almost) never need to worry about that • Just don’t forget the star, when declaring variables or parameters
42. Foundation • The “standard library” of Objective-C
43. Ruby String
44. Objective-C NSString
45. Ruby Array
46. Objective-C NSArray
47. Ruby Hash
48. Objective-C NSDictionary
49. Objective-C NSMutableString NSMutableArray NSMutableDictionary
50. Ruby names = ['Mikael', 'Kristofer', 'Lukas'] ! name = names[1]
51. Objective-C NSArray *names = @[@"Mikael", @"Kristofer", @“Lukas”]; ! NSString *name = names[1];
52. Ruby locations = { 'Mikael' => 'Vienna', 'Kristofer' => 'Istanbul', 'Lukas' => 'Istanbul' } ! location = locations['Kristofer']
53. Objective-C NSDictionary *locations = @{ @"Mikael": @"Vienna", @"Kristofer": @"Istanbul", @"Lukas": @"Istanbul" }; ! NSString *location = locations[@"Kristofer"];
54. Why NS, KM, etc.?
55. • Objective-C doesn’t have proper namespaces • We use 2 or 3 letters to prefix all class names to prevent clashes • For example, the Foundation framework that defines strings, arrays, hashes etc. uses “NS” • “NS” stands for “NeXTSTEP” Prefixing classes
56. Duck typing and introspection
57. Duck typing When I see a bird that walks like a duck and swims like a duck and quacks like a duck, I call that bird a duck.
58. Ruby sender.respond_to?(:to_f)
59. Objective-C [sender respondsToSelector:@selector(floatValue)];
60. Ruby def action(sender) if sender.class == Array # ... elsif sender.class == Hash # ... end end
61. Objective-C - (void)action:(id)sender { if ([sender isKindOfClass:[UIButton class]]) { // ... } else if ([sender isKindOfClass:[UITapGestureRecognizer class]]) { // .. } }
62. Blocks
63. Block • Enumeration • Passing code around • Async tasks, completion handlers • Blocks are closures
64. Ruby block = lambda { puts 'hello, world' } ! block.call
65. Objective-C void (^block)() = ^ { NSLog(@"hello, world"); }; ! block();
66. Grand Central Dispatch dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0); ! dispatch_async(queue, ^ { // Long background task ! dispatch_async(dispatch_get_main_queue(), ^ { // Update the UI }); });
67. How Do I Declare A Block in Objective-C? http://fuckingblocksyntax.com
68. Domain Specific Languages
69. Ruby (Bacon) describe 'A new array' do before do @ary = Array.new end it 'should be empty' do @ary.should.be.empty @ary.should.not.include 1 end end
70. Objective-C (Kiwi) describe(@"Team", ^ { context(@"when newly created", ^ { it(@"should have a name", ^ { id team = [Team team]; [[[team name] should] equal:@"Black Hawks"]; }); it(@"should have 11 players", ^ { id team = [Team team]; [[[team should] have:11] players]; }); }); });
71. The Objective-C Runtime
72. The Objective-C Runtime #include <objc/runtime.h>
73. The Objective-C Runtime • objc_msgSend • class_getMethodImplementation • objc_allocateClassPair • objc_getClassList • etc.
74. Tools
75. rubygems and bundler # Gemfile ! source 'https://rubygems.org' ruby '2.1.0' ! gem 'rack' gem 'vienna', '>= 0.4.0' gem 'thin'
76. Cocoapods # Podfile ! platform :ios, '7.0' ! pod 'AFNetworking', '~> 2.0'
77. Where to Go from Here
78. Around the Web • iOS Developer Library • raywenderlich.com • Cocoapods
79. Books • Objective-C Programming: The Big Nerd Ranch Guide • iOS Programming: The Big Nerd Ranch Guide • iOS 7 Programming Fundamentals • Programming iOS 7
80. Thank You! • @mkonutgan on Twitter • @kmikael on GitHub • kmikael.com • me@kmikael.com