Swift and Kotlin

If you write code in Objective C or Java, Swift and Kotlin will make you happy.

Transcript

1. func main(args: Array<String>) { print("Hello, " + args[0]) } fun main(args: Array<String>) { println("Hello, " + args[0]) }
2. If you write code in Objective C or Java, Swift and Kotlin will make you happy.
3. Type Inference 1
4. DDXMLElement *element = [DDXMLElement elementWithName:@"iq"];
5. Packet packet = new Packet("iq");
6. DDXMLElement *element = [DDXMLElement elementWithName:@"iq"]; much element such long Wow IDE
7. let element = DDXMLElement(name: "iq")
8. val packet = Packet("iq")
9. Immutablity is an easily expressible first class citizen of the type system. let packet = Packet("iq") var packet = Packet("iq") val packet = Packet("iq") var packet = Packet("iq")
10. The compiler will not let you write code that can crash because of nulls. 2
11. NSURL *url = [NSURL URLWithString:myString]; NSURLRequest *request = [NSURLRequest requestWithURL:url];
12. NSString *string = @”sunshine”; NSURL *url = [NSURL URLWithString:myString]; NSURLRequest *request = [NSURLRequest requestWithURL:url];
14. let myString = "sunshine" let url = URL(string: myString) let request = URLRequest(url: url)
16. struct URL { init?(string: String): URL? } struct URLRequest { init(url: URL) }
17. // String -> URL? let url: URL? = URL(string: myString) // URL -> URLRequest let request = URLRequest(url: url)
18. Guess what’s the Kotlin syntax
19. But it won’t get in your way when you write the happy path. 3
20. person?.family?.meet()
21. let marriedGuy = person as? MarriedGuy if (marriedGuy) { marriedGuy.wife.family?.meet() }
22. (person ?: otherPerson).family?.meet()
23. Bang bang when you know* it won’t bang bang. !! * Are you sure?
24. Guess what’s the Kotlin syntax
25. Why is ?: called* the Elvis operator? Quiz * “Nil/Null Coalescing”, cause Elvis is too cool for official documentation
26. guard let marriedGuy = person as? MarriedGuy else { return “Did you even read the docs?” } marriedGuy.wife.family?.meet()
27. Kotlin kills it here
28. if (person !is MarriedGuy) { return “Did you even read the docs?” } person.wife.family?.meet()
29. fun oh(missingPerson: Person?): String { if (missingPerson == null) { return “Nobody’s missing” } return missingPerson.name() + “ got lost” }
30. when (x) { is Int -> print(x + 1) is String -> print(x.length + 1) is IntArray -> print(x.sum()) } * Example taken from Kotlin docs
31. Why is less code better? Quiz
32. This is just boilerplate code obsuring the fact that we want to, yes really want to, oh here is another legacy annotation! return a buggy racecar from this function. This function returns a buggy racecar.
33. The lesser code is not because of a less powerful language. In fact, the Swift and Kotlin compilers work with richer semantics when parsing your code. They just do the grunt work for you.
34. Lambdas 4
35. dispatch_async(queue, ^{ // do stuff });
36. Queue.async { // do stuff }
37. new Thread() { @Override public void run() { // do stuff }; };
38. new Thread(() -> { // do stuff }); Java 8 / Android with Retrolambda
39. Thread { // do stuff }
40. There is not even a single* spurious character. * Unless you go Python
41. Unlike Java 8, Kotlin gives you “real” lambdas. PS:
42. Value Types 5
43. Is a person a value or a object? Why does it matter? Quiz
44. @interface Person : NSObject @property (nonatomic, readonly) NSString *name; @property (nonatomic) NSInteger age; @end @implementation Person - (instancetype)initWithName:(NSString *)name age:(NSInteger)age { self = [super init]; if (self) { _name = name; _age = age; } return self; } @end
45. Objective C folks: Did we miss something? Quiz
46. @implementation Person - (BOOL)isEqualToPerson:(Person *)person { return [self.name isEqual:person.name] && self.age == person.age; } - (BOOL)isEqual:(id)object { if (self == object) { return YES; } if (![object isKindOfClass:[Person class]]) { return NO; } return [self isEqualToPerson:(Person *)object]; } - (NSUInteger)hash { return [self.name hash] ^ (unsigned long)self.age; } @end
47. We done? Quiz
48. @implementation Person - (NSString *)description { return [NSString stringWithFormat: @"Person(name: %@, age: %@)", self.name, @(self.age)]; } @end Total: 41 Lines
49. class Person { private final String name; private final int age; Person(String name, int age) { this.name = name; this.age = age; } public String getName() { return name; } public int getAge() { return age; } @Override public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; Person person = (Person) o; if (getAge() != person.getAge()) return false; return getName() != null ? getName().equals(person.getName()) : person.getName() == null; } @Override public int hashCode() { int result = getName() != null ? getName().hashCode() : 0; result = 31 * result + getAge(); return result; } @Override public String toString() { return "Person{" + "name='" + name + '\'' + ", age=" + age + '}'; } } 51 Lines
50. @Data class Person { private final String name; private final int age; } Lombok!
51. struct Person { let name: String let age: Int } let dude = Person(name: "Dude", age: 21)
52. data class Person( val name: String, val age: Int) val dude = Person(name = "Dude", age = 21)
53. There is not a single spurious line.
54. What is the difference between equality and identity? Quiz Flashback
55. dude = = otherDude [dude isEqual:otherDude] Equality
56. dude = = = otherDude dude = = otherDude Identity
57. Guess what’s the Kotlin syntax
58. Who inspired Whom? Aside
59. What does “Kotlin” mean? Quiz
60. DSLs Meta
61. How hard do you think it is to implement CocoaPods or Gradle? Quiz
62. Ruby Groovy Swift Kotlin Rake CocoaPods Capistrano Gradle
63. With the inessentials stripped out, you can structure your own code such that it reads as if it were using a DSL. “Code that reads like Pseudo Code”
64. Mixins 6
65. protocol Duck { func quack() -> String } extension Duck { func quack() -> String { return "quack" } }
66. struct WeirdPerson: Person, Duck { } Person().quack()
67. interface Duck { fun quack() = "quack" } class WeirdPerson: Person, Duck { } * This works in Java 8 too
68. Extensions 7
69. public class StringUtils { public static String developerize(String s) { return "Basically, " + s; } } StringUtils.developerize(“hello”)
70. Objective C audience right now
71. fun String.developerize() = "Basically, " + this “hello”.developerize()
72. NSInteger TDTIntegerSquare(NSInteger x) { return x * x; } TDTIntegerSquare(5);
73. extension Int { func square() -> Int { return self * self } } 5.square()
74. Modern Standard Libraries 8
75. let bhais = persons .filter { $0.car.color == .red } .sorted(by: {$0.swag > $1.age}) .prefix(upTo: 3) .map { $0.name }
76. val bhais = persons .filter { it.car.color == Color.RED } .sortedBy { it.swag } .take(3) .map { it.name }
77. Seamless interop with Objective-C/Java collections types.
78. Swift has sugar for collections. Kotlin, unfortunately, doesn’t.
79. Random feature, so that Kotlin doesn’t feel bad...
80. Car makeCarForBhai() { Car *car = Car(); car.color = Color.RED; car.installNitroBoost(); car.removeSilencer(); return car; }
81. fun makeCarForBhai(): Car { return Car().apply { color = Color.RED installNitroBoost() removeSilencer() } } * Swift: The “Then” library
82. More goodies than one can pack in 10. Meta
83. • (Swift) Generics • (Kotlin) Better Generics • Lazy Properties • Observable Properties • Real Enumerations • (Kotlin) Try with Resource Blocks • (Swift) Booleans! • Ranges • String Interpolation • Operator Overloading • Easier Singletons
84. Singletons 9
85. @interface God: NSObject + (God *)sharedInstance; @end @implementation God + (God *)sharedInstance { static God *sharedInstance; static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ sharedInstance = [[God alloc] init]; }); return sharedInstance; } @end * Almost
86. class God { static let sharedInstance = God() } * Almost
87. class God { static let sharedInstance = God() private init() {} }
88. class God { private static final God instance = new God(); private God() {} public static God getInstance() { return instance; } } * Almost
89. class God { private static final God instance = null; private God() {} public static synchronized God getInstance() { if (instance == null) instance = new God(); return instance; } }
90. object God { }
91. The partying can start now! 10
92. 1. Create a “.swift” file Xcode: "Would You like to configure an Objective-C bridging Header"? You: Yes 2. Build Settings > Defines Module > Yes 3. #import "YourProjectName-swift.h"
93. 1. Create a “.kt” file Android Studio: "Install Kotlin Plugin"? You: Yes 2. ⌘⇧A “Configure Kotlin in Project” 3. Gradle “Sync Now”
94. No Runtime Overhead Swift compiles to native code, Kotlin compiles to JVM bytecode.
95. You can literally copy paste Java code from StackOverflow. Kotlin Extras
96. Until Swift 4, your apps will embed the Swift runtime. Depending on the frameworks you use, this can be substantial increase in your binary size (think ~5 MB). ⚠ Dragons * Kotlin’s fine. ~900K pre-proguard.
97. The Kotlin compiler is visibly slower than Java’s. Kotlin supports incremental builds, but your clean builds will take much longer once you have a lot of Kotlin files. ⚠ Dragons * Swift’s fine.
98. Swift, because Apple. Kotlin, because Retrolambda+Lombok+Guava. Pragmatics
99. if (convinced) { manager.pester() } else { discuss(Date.now()) }