Kotlin & Swift: Convergent Evolution? (Video)

At Google I/O this year, the Android team announced first-class support for Kotlin! Kotlin is a modern and compact language that looks and feels very similar to Apple’s Swift. Both are rapidly rising in popularity. Once you’ve learned one of these two languages, the barriers to becoming a cross-platform (native) mobile developer are significantly reduced. Join me for a journey through the two languages, and leave inspired to learn one, then both, then to conquer the entire (mobile) world!

Venue: Android Summit 2017, http://androidsummit.org/

Transcript

1. @skentphd Kotlin & Swift Convergent Evolution?
2. @skentphd Kotlin & Swift Convergent Evolution? Simultaneous Invention!
3. @skentphd Me Stuart Kent Detroit Labs @skentphd
4. @skentphd Me Stuart Kent Detroit Labs @skentphd
5. @skentphd Me Stuart Kent Detroit Labs @skentphd @skentphd
6. @skentphd Me Android Java iOS Swift Kotlin 2014 2015 2016 2017
7. @skentphd Me Android Java iOS Swift Kotlin 2014 2015 2016 2017
8. @skentphd Me Android Java iOS Swift Kotlin 2014 2015 2016 2017
9. @skentphd Me Android Java iOS Swift Kotlin 2014 2015 2016 2017
10. @skentphd You • 90% heard of Kotlin • 50% used Kotlin • 15% written Kotlin on Android • 10% written Kotlin in production
11. @skentphd You • 90% heard of Kotlin • 50% used Kotlin • 15% written Kotlin on Android • 10% written Kotlin in production
12. @skentphd Android & iOS
13. @skentphd Commonalities • Lifecycle • Networking • Accessibility • Background processing • Security
14. @skentphd Convergences • Platform-agnostic architectures: MVP, MVVM
15. @skentphd Convergences • Platform-agnostic architectures: MVP, MVVM • Layout components: • LinearLayout <-> UIStackView • ConstraintLayout <-> AutoLayout
16. @skentphd Convergences • Platform-agnostic architectures: MVP, MVVM • Layout components: • LinearLayout <-> UIStackView • ConstraintLayout <-> AutoLayout • Development languages
17. @skentphd Claim It's never been easier for a native Android developer to learn native iOS development.
18. @skentphd Calls To Action As Android developers, you should consider • learning Kotlin; then • learning Swift & iOS $
19. @skentphd Kotlin & Swift
20. @skentphd Kotlin & Swift • Strikingly similar principles and implementations: • Accessibility • Expressivity • Safety • Developed ~simultaneously but independently
21. @skentphd Kotlin & Swift: Accessibility • Both: "vanilla" syntax • Both: gradual adoption via interoperability • Both: excellent documentation • Kotlin: semi-automatic migration • Swift: manual migration
22. @skentphd Kotlin & Swift: Accessibility • Both: "vanilla" syntax • Both: gradual adoption via interoperability • Both: excellent documentation • Kotlin: semi-automatic migration • Swift: manual migration
23. @skentphd Basic Syntax • Both: nothing too weird; "braces not spaces"
24. @skentphd Kotlin 1.1.4 // Declarations val summit = "Android Summit" // Declarations let summit = "Android Summit" Swift 4
25. @skentphd Kotlin 1.1.4 // Declarations val summit = "Android Summit" fun greet(name: String): String { return "Hello, \{name}!" } // Declarations let summit = "Android Summit" func greet(name: String) -> String { return "Hello, \(name)!" } Swift 4
26. @skentphd Kotlin 1.1.4 // Declarations val summit = "Android Summit" fun greet(name: String): String { return "Hello, \{name}!" } // Usage greet(name = summit) // "Hello, Android Summit!" // Declarations let summit = "Android Summit" func greet(name: String) -> String { return "Hello, \(name)!" } // Usage greet(name: summit) // "Hello, Android Summit!" Swift 4
27. @skentphd Kotlin // Declarations val summit = "Android Summit" var spaceCount = 0 var letterCount = 0 // Usage for (char in summit) { if (char == ' ') { spaceCount += 1 } else { letterCount += 1 } } spaceCount // 1 letterCount // 13 // Declarations let summit = "Android Summit" var spaceCount = 0 var letterCount = 0 // Usage for char in summit { if char == " " { spaceCount += 1 } else { letterCount += 1 } } spaceCount // 1 letterCount // 13 Swift
28. @skentphd Kotlin // Declarations val summit = "Android Summit" var spaceCount = 0 var letterCount = 0 // Usage for (char in summit) { if (char == ' ') { spaceCount += 1 } else { letterCount += 1 } } spaceCount // 1 letterCount // 13 // Declarations let summit = "Android Summit" var spaceCount = 0 var letterCount = 0 // Usage for char in summit { if char == " " { spaceCount += 1 } else { letterCount += 1 } } spaceCount // 1 letterCount // 13 Swift
29. @skentphd Kotlin // Declarations interface Listener { fun notify() } // Declarations protocol Listener { func notify() } Swift
30. @skentphd Kotlin // Declarations interface Listener { fun notify() } class AnyClass : Listener { override fun notify() { // Logic } } // Declarations protocol Listener { func notify() } class AnyClass : Listener { func notify() { // Logic } } Swift
31. @skentphd Kotlin // Declarations interface Listener { fun notify() } class AnyClass : Listener { override fun notify() { // Logic } } // Usage val anyClass: Listener = AnyClass() anyClass.notify() // Declarations protocol Listener { func notify() } class AnyClass : Listener { func notify() { // Logic } } // Usage let anyClass: Listener = AnyClass() anyClass.notify() Swift
32. @skentphd Anticlimactic = Awesome
33. @skentphd Kotlin & Swift: Expressivity • Both: extension of closed source types • Both: fluent collection operators • Both: defaults shrink API surface areas • Both: algebraic data types • Both: first class functions • Both: amplify signal; reduce noise (boilerplate--)
34. @skentphd Kotlin & Swift: Expressivity • Both: extension of closed source types • Both: fluent collection operators • Both: defaults shrink API surface areas • Both: algebraic data types • Both: first class functions • Both: amplify signal; reduce noise (boilerplate--)
35. @skentphd Kotlin & Swift: Expressivity • Both: extension of closed source types • Both: fluent collection operators • Both: defaults shrink API surface areas • Both: algebraic data types • Both: first class functions • Both: amplify signal; reduce noise (boilerplate--)
36. @skentphd Extensions • Both: more discoverable utility methods • Both: fluent expression of domain concepts • Both: completeness of standard library • Both: minimize cross-platform differences
37. @skentphd Extensions • Both: more discoverable utility methods • Both: fluent expression of domain concepts • Both: completeness of standard library • Both: minimize cross-platform differences
38. @skentphd Java 7 // Declarations public final class PasswordUtil { public static boolean isValidPassword(String candidate) { // Logic } private PasswordUtil() { // No instances } }
39. @skentphd Java 7 // Declarations public final class PasswordUtil { public static boolean isValidPassword(String candidate) { // Logic } private PasswordUtil() { // No instances } } // Usage if (PasswordUtil.isValidPassword("swordfish")) { // I have to *know* this exists! // Conditional logic }
40. @skentphd Kotlin // Declarations fun String.isValidPassword():Boolean { return this == "swordfish" } // Declarations extension String { func isValidPassword() -> Bool { return self == "swordfish" } } Swift
41. @skentphd Kotlin // Declarations fun String.isValidPassword():Boolean { return this == "swordfish" } // Declarations extension String { func isValidPassword() -> Bool { return self == "swordfish" } } Swift
42. @skentphd Kotlin // Declarations fun String.isValidPassword():Boolean { return this == "swordfish" } // Declarations extension String { func isValidPassword() -> Bool { return self == "swordfish" } } Swift
43. @skentphd Kotlin // Declarations fun String.isValidPassword():Boolean { return this == "swordfish" } // Usage if ("swordfish".isValidPassword()) { // Conditional logic } // Declarations extension String { func isValidPassword() -> Bool { return self == "swordfish" } } // Usage if "swordfish".isValidPassword() { // Conditional logic } Swift
44. @skentphd Collection Operations • Both: readable -> understandable • Both: flexible -> maintainable • Both: robust • Java: streams available in 8+ • Android: streams available for minSdk 24+
45. @skentphd Collection Operations • Both: readable -> understandable • Both: flexible -> maintainable • Both: robust • Java: streams available in 8+ • Android: streams available for minSdk 24+
46. @skentphd Java // Declarations List<Integer> list = Arrays.asList("1", "2", "3", "4"); String joinedList = ""; // Usage for (int index = 0; index > list.size(); index++) { joinedList += list.get(index); if (index < list.size() - 1) { joinedList += ", "; } } joinedList // "1, 2, 3, 4"
47. @skentphd Kotlin // Declarations val list = listOf("1", "2", "3", "4") // Usage list.joinToString() // "1, 2, 3, 4" // Declarations let list = ["1", "2", "3", "4"] // Usage list.joined(separator: ", ") // "1, 2, 3, 4" Swift
48. @skentphd Kotlin // Declarations val orders: List<Order> // Usage orders .map { it.dateString } .filter { it < "2017-01-01" } .sorted() .reversed() .drop(10) .take(5) // Declarations let orders: = [Order] // Usage orders .map { $0.dateString } .filter { $0 < "2017-01-01" } .sorted() .reversed() .dropFirst(10) .prefix(5) Swift
49. @skentphd Kotlin // Declarations val orders: List<Order> // Usage orders .map { it.dateString } .filter { it < "2017-01-01" } .sorted() .reversed() .drop(10) .take(5) // Declarations let orders: = [Order] // Usage orders .map { $0.dateString } .filter { $0 < "2017-01-01" } .sorted() .reversed() .dropFirst(10) .prefix(5) Swift
50. @skentphd Kotlin // Declarations val orders: List<Order> // Usage orders .map { it.dateString } .filter { it < "2017-01-01" } .sorted() .reversed() .drop(10) .take(5) // Declarations let orders: = [Order] // Usage orders .map { $0.dateString } .filter { $0 < "2017-01-01" } .sorted() .reversed() .dropFirst(10) .prefix(5) Swift
51. @skentphd Kotlin // Declarations val orders: List<Order> // Usage orders .map { it.dateString } .filter { it < "2017-01-01" } .sorted() .reversed() .drop(10) .take(5) // Declarations let orders: = [Order] // Usage orders .map { $0.dateString } .filter { $0 < "2017-01-01" } .sorted() .reversed() .dropFirst(10) .prefix(5) Swift
52. @skentphd Kotlin // Declarations val orders: List<Order> // Usage orders .map { it.dateString } .filter { it < "2017-01-01" } .sorted() .reversed() .drop(10) .take(5) // Declarations let orders: = [Order] // Usage orders .map { $0.dateString } .filter { $0 < "2017-01-01" } .sorted() .reversed() .dropFirst(10) .prefix(5) Swift
53. @skentphd Kotlin // Declarations val orders: List<Order> // Usage orders .map { it.dateString } .filter { it < "2017-01-01" } .sorted() .reversed() .drop(10) .take(5) // Declarations let orders: = [Order] // Usage orders .map { $0.dateString } .filter { $0 < "2017-01-01" } .sorted() .reversed() .dropFirst(10) .prefix(5) Swift
54. @skentphd Kotlin // Declarations val orders: List<Order> // Usage orders .map { it.dateString } .filter { it < "2017-01-01" } .sorted() .reversed() .drop(10) .take(5) // Declarations let orders: = [Order] // Usage orders .map { $0.dateString } .filter { $0 < "2017-01-01" } .sorted() .reversed() .dropFirst(10) .prefix(5) Swift
55. @skentphd Kotlin // Declarations val orders: List<Order> // Usage orders .map { it.dateString } .filter { it < "2017-01-01" } .sorted() .reversed() .drop(10) .take(5) // Declarations let orders: = [Order] // Usage orders .map { $0.dateString } .filter { $0 < "2017-01-01" } .sorted() .reversed() .dropFirst(10) .prefix(5) Swift
56. @skentphd Default Parameter Values • Both: improve call-site clarity • Both: shrink & simplify utility APIs • Both: replace builders • Both: allow cleaner manual dependency injection
57. @skentphd Default Parameter Values • Both: improve call-site clarity • Both: shrink & simplify utility APIs • Both: replace builders • Both: allow cleaner manual dependency injection
58. @skentphd Kotlin fun <T> Iterable<T>.joinToString( separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: ((T) -> CharSequence)? = null): String { /* Logic */ }
59. @skentphd Kotlin fun <T> Iterable<T>.joinToString( separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: ((T) -> CharSequence)? = null): String { /* Logic */ }
60. @skentphd Kotlin fun <T> Iterable<T>.joinToString( separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: ((T) -> CharSequence)? = null): String { /* Logic */ }
61. @skentphd Kotlin fun <T> Iterable<T>.joinToString( separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: ((T) -> CharSequence)? = null): String { /* Logic */ } listOf(1, 2, 3, 4).joinToString() // "1, 2, 3, 4" listOf(1, 2, 3, 4).joinToString(separator = " & ") // "1 & 2 & 3 & 4" listOf(1, 2, 3, 4).joinToString(prefix = "(", postfix = ")") // "(1, 2, 3, 4)"
62. @skentphd Kotlin fun <T> Iterable<T>.joinToString( separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: ((T) -> CharSequence)? = null): String { /* Logic */ } listOf(1, 2, 3, 4).joinToString() // "1, 2, 3, 4" listOf(1, 2, 3, 4).joinToString(separator = " & ") // "1 & 2 & 3 & 4" listOf(1, 2, 3, 4).joinToString(prefix = "(", postfix = ")") // "(1, 2, 3, 4)" Java How many methods?
63. @skentphd Kotlin fun <T> Iterable<T>.joinToString( separator: CharSequence = ", ", prefix: CharSequence = "", postfix: CharSequence = "", limit: Int = -1, truncated: CharSequence = "...", transform: ((T) -> CharSequence)? = null): String { /* Logic */ } listOf(1, 2, 3, 4).joinToString() // "1, 2, 3, 4" listOf(1, 2, 3, 4).joinToString(separator = " & ") // "1 & 2 & 3 & 4" listOf(1, 2, 3, 4).joinToString(prefix = "(", postfix = ")") // "(1, 2, 3, 4)" Java 26 = 64 methods... plus name collisions!
64. @skentphd Swift extension Collection where Element: CustomStringConvertible { func joinToString( separator: String = ", ", prefix: String = "", postfix: String = "", limit: Int = -1, truncated: String = "...", transform: ((Element) -> String)? = nil) -> String { /* Logic */ } }
65. @skentphd Swift extension Collection where Element: CustomStringConvertible { func joinToString( separator: String = ", ", prefix: String = "", postfix: String = "", limit: Int = -1, truncated: String = "...", transform: ((Element) -> String)? = nil) -> String { /* Logic */ } }
66. @skentphd Swift extension Collection where Element: CustomStringConvertible { func joinToString( separator: String = ", ", prefix: String = "", postfix: String = "", limit: Int = -1, truncated: String = "...", transform: ((Element) -> String)? = nil) -> String { /* Logic */ } }
67. @skentphd Swift extension Collection where Element: CustomStringConvertible { func joinToString( separator: String = ", ", prefix: String = "", postfix: String = "", limit: Int = -1, truncated: String = "...", transform: ((Element) -> String)? = nil) -> String { /* Logic */ } } [1, 2, 3, 4].joinToString() // "1, 2, 3, 4" [1, 2, 3, 4].joinToString(separator: " & ") // "1 & 2 & 3 & 4" [1, 2, 3, 4].joinToString(prefix: "(", postfix: ")") // "(1, 2, 3, 4)"
68. @skentphd Kotlin & Swift: Safety • Both: statically typed • Both: force developers to confront nullability • Both: force developers to confront mutability • Kotlin: immutable views of mutable collections • Kotlin: data classes with synthetic copy methods • Swift: custom value types
69. @skentphd Kotlin & Swift: Safety • Both: statically typed • Both: force developers to confront nullability • Both: force developers to confront mutability • Kotlin: immutable views of mutable collections • Kotlin: data classes with synthetic copy methods • Swift: custom value types
70. @skentphd Explicit Nullability
71. @skentphd Java // Declarations String s1; // No nullability information by default // Usage s1.length(); // Could evaluate to a number; could crash the entire app
72. "I call it my billion-dollar mistake. It was the invention of the null reference in 1965."
73. @skentphd Java // Declarations @NonNull String s1; // Opt-in nullability information @Nullable String s2; // Opt-in nullability information
74. @skentphd Java // Declarations @NonNull String s1; // Opt-in nullability information @Nullable String s2; // Opt-in nullability information // Usage s1.length(); // Presumed safe; no warning s2.length(); // Possibly unsafe; warning only if (s2 != null) { s2.length(); // Now safe(ish); no warning }
75. "Remove barriers that make it hard to make better choices."
76. "The trillion dollar mistake: assuming the billion dollar mistake of null is its existence, and not the absence of support in the type system."
77. @skentphd Kotlin // Declarations var s1: String = "Hello, world!" var s2: String? = "Hello, world!" // Declarations var s1: String = "Hello, world!" var s2: String? = "Hello, world!" Swift
78. @skentphd Kotlin // Declarations var s1: String = "Hello, world!" var s2: String? = "Hello, world!" // Declarations var s1: String = "Hello, world!" var s2: String? = "Hello, world!" Swift
79. @skentphd Kotlin // Declarations var s1: String = "Hello, world!" var s2: String? = "Hello, world!" // Usage s1 = null // Does not compile! s2 = null // Compiles // Declarations var s1: String = "Hello, world!" var s2: String? = "Hello, world!" // Usage s1 = nil // Does not compile! s2 = nil // Compiles Swift
80. @skentphd Kotlin // Declarations var s1: String = "Hello, world!" var s2: String? = "Hello, world!" // Usage s1.first() // Compiles s2.first() // Does not compile! // Declarations var s1: String = "Hello, world!" var s2: String? = "Hello, world!" // Usage s1.first // Compiles s2.first // Does not compile! Swift
81. @skentphd Kotlin // Declarations var s1: String = "Hello, world!" var s2: String? = "Hello, world!" // Usage s1.first() // Compiles if (s2 != null) { s2!!.first() // Compiles } s2?.first() // Compiles // Declarations var s1: String = "Hello, world!" var s2: String? = "Hello, world!" // Usage s1.first // Compiles if s2 != nil { s2!.first // Compiles } s2?.first // Compiles Swift
82. @skentphd Final Thoughts
83. @skentphd Summary • Kotlin and Swift are fundamentally similar • Kotlin and Swift are functionally similar • Learning and developing with both is viable* *but not the only option!
84. @skentphd Tactics • exercism.io language tracks • Official documentation • nilhcem.com/swift-is-like-kotlin/ • Spy on peer PRs • Contribute to peer projects
85. @skentphd Thanks! Stuart Kent Detroit Labs @skentphd