The Secret Life of Types in Swift

Types are important? Yes they are! And they can form the whole behaviour of a language - like Swift. This talk deals with the very type essentials and gives a first glance under the hood of the Swift type system.

Transcript

1. Manuela Rink Technical Evangelist @ The secret life of types in Swift
2. What is Swift?
3. Swift?
4. Swift?!!?
5. Swift!!!
6. Disclaimer At least intermediate experience with reading and writing different programming languages and a basic understanding of type systems. Yes, we will see code – because programming! ~LVL300-400 It’s not impolite to leave now – no kitten memes to miss here!
7. The Language
8. v4 One-side ranges Comfortable encoding/decoding Multi-line string literals Improved key-value coding Strings as collections More powerful dictionaries Downwards compatibility*
9. Compiler version bound to Xcode version 2014-08-18 Swift 1.0 2014-10-16 Swift 1.1 2015-04-08 Swift 1.2 2015-09-16 Swift 2 2015-10-20 Swift 2.1 2015-12-03 open sourced 2016-03-21 Swift 2.2 2016-06-12 Swift 2.3 2016-09-13 Swift 3 * 2016-10-27 Swift 3.0.1 * Compiler for Swift 3 and 2.3 offered in Xcode 8 Code adjustments No downwards compatiblity
10. IEEE Spectrum Language Ranking 2017 https://spectrum.ieee.org/computing/software/the-2017-top-programming-languages IEEE Spectrum Overall Readers
11. IEEE Spectrum Language Ranking 2017 https://spectrum.ieee.org/computing/software/the-2017-top-programming-languages IEEE Spectrum Trending
12. IEEE Spectrum Language Ranking 2017 https://spectrum.ieee.org/computing/software/the-2017-top-programming-languages IEEE Spectrum Mobile only
13. ? no fixed ABI with v3.0.1 update IDE – adapt code compatibility with Swift based frameworks
14. The good old… Named parameters Structs and Enums Blocks/Closures Automatic memory management The shiny new… Inferred types Modules make headers obsolete By default nothing can be nil Tuples & multiple return values
15. The sugar No semicolon Byebye (most of you) square brackets The promise Swift code is save by design. Lightning fast … and fun to learn because of its shortness!
16. ?! ! ? !!!!11eleven !? ? ? ! ? ? ! ? ! ? ! ? TYPES TYPES EVERYWHERE
17. It’s all about types
19. There shall be $noRoot and never will there be nil* Swift doesn’t have a specific root type like e.g. Obj-C, Java… Empty values are not allowed* *almost
20. Obj-C Java java.lang.Object java.lang.Number java.lang.Integer conforms to: Serializable, Comparable<Integer> NSObject NSValue NSNumber conforms to: CKRecordCalue, CVarArg, Equatable, ExpressibleByBooleanLiteral, ExpressibleByFloatLiteral, ExpressibleByIntegerLiteral, Hashable, NSFetchRequestResult conforms to: BitwiseOperations, CVarArg, Comparable, CustomPlaygroundQuickLookable, CustomReflectable, CustomStringConvertible, Equatable, ExpressibleByIntegerLiteral, Hashable, Integer, IntegerArithmetic, MirrorPath, SignedInteger, SignedNumber, Strideable, _Incrementable, _Integer, _IntegerArithmetic, _SignedInteger Swift Int
21. Int Type in Swift http://swiftdoc.org/v3.1/
22. Float Dictionary http://swiftdoc.org/v3.1/
23. Dive into types
24. No dedicated type root Type conforms to protocols instead of heavy inheritance Super loose coupling Nice separation of concerns Clean architecture … and there are just two types of types! Named types & compound types* *which can contain named types
26. Named Types
27. Named types have ... names!
28. … } Int gets extended by a lot of other types. Conforming protocol list is rather short. But conforming / inheritance hierarchy is quite complex. Extend to your needs!
29. Int Type in Swift http://swiftdoc.org/v3.1/
30. Compound Types
31. Compound types have … no names And that’s a good thing!
32. var greatTuple = (x: 10, y: 20) greatTuple = (x: 12, y: 50) greatTuple = (0,0) print (greatTuple.0 + “==“ + greatTuple.x) greatTuple = (xCoord: 10, yCoord: 20) greatTuple = (x: “manu”, y: 20) Tuple Type Ad hoc type definition for named multiple values with type safety
33. func randomColorScheme () -> (fg: UIColor, bg: UIColor) { let foreground = randomForegroundColor() let background = randomBackgroundColor() return (foreground, background) } let colorScheme = randomColorScheme() view.backgroundColor = colorScheme.bg Tuple Type Use to return multiple values from a function
34. var point = (13, 12) typealias Point = (Int, Int) var point = Point(10, 12) typealias Point = (x: Int, y: Int) var myPoint = Point(x: 10, y: 12) var myOtherPoint = Point(10, 12) var myRealPoint = (10, 12) typealias CGPoint = (String, String) var thePoint = CGPoint(“this is”, “dangerous”) Tuple Type Give them names… … with typealias
35. () It’s Void! public typealias Void = () let myAge : (Int) = (23) let myAge : Int = 23 (Type) == Type
36. func processPerson (withID: Int) -> () {} func processVIP (withID: Int) {} struct Person { firstname : String lastname : String } func nameForPerson (withID: Int) -> (name: String, age: Int) {} func nameForPerson (withID: Int) -> (Person) {} func nameForPerson (withID: Int) -> Person {} func detailsForPerson (withID: Int) -> (obj: Person, age: Int) {} Function Type Defines the type of a function or method. Combines the parameter and return type with -> Can be composed of named and compound types again
37. func whereToGo (ahead : Bool) -> (Int) -> Int { func goAhead (input: Int) -> Int { return input + 1 } func goBack (input: Int) -> Int { return input - 1 } return ahead ? goAhead : goBack } var stepsToHome = -3 let goHome = whereToGo(ahead: stepsToHome < 0) while stepsToHome != 0 { print("steps to home: \(abs(stepsToHome))") stepsToHome = goHome(stepsToHome) } Function Type Global functions vs. nested functions… … and their strange looking return types. (Bool) -> (Int) -> Int in inner in out
38. Use functions on variables func goHome (ahead: Bool) {} func stepsToHome () -> Int { return steps } var f = goHome f = stepsToHome // type of f is (Bool) -> Void Variadic parameters as arrays func printAll(_ numbers: Int...) -> Int { for number in numbers { print ( “the number \(number)”) } }
39. Closures parent concept of global and nested functions { (parameters) -> return type in // do funky stuff } let names = [”Igor”, ”Horst”, ”Manu”, ”Alex”, ”David”] func ascending (_ s1: String, _ s2: String) -> Bool { return s1 < s2 } var ascendingNames = names.sorted(by: ascending) ascendingNames = names.sorted(by: { (s1: String, s2: String) -> Bool in return s1 < s2 }) ascendingNames = names.sorted(by: { s1, s2 in s1 < s2}) ascendingNames = names.sorted(by: {$0 < $1}) Shorten your code (at the expense of readability) ascendingNames = names.sorted(by: <)
40. http://fuckingblocksyntax.com/ http://fuckingclosuresyntax.com/
41. the sugar on the top
42. ?! Don’t be afraid … it’s just Optionals public enum ImplicitlyUnwrappedOptional<Wrapped> : ExpressibleByNilLiteral { /// The absence of a value. Typically written using the nil literal, `nil`. case none /// The presence of a value, stored as `Wrapped`. case some(Wrapped) /// Creates an instance that stores the given value. public init(_ some: Wrapped) /// Creates an instance initialized with `nil`. /// /// Do not call this initializer directly. It is used by the compiler when /// you initialize an `Optional` instance with a `nil` literal. For example: /// let i: Index! = nil public init(nilLiteral: ()) }
43. var myName : Optional<String> myName = "manu” var theName = “manu” if myName != nil && theName != nil { print(myName) print(theName) } “Optional(“manu”)” “manu”
44. var myName : String? = “manu” print(myName) print(myName!) if let name = myName { print(name) } “Optional(“manu”)” “manu” “manu”
45. var name : String? = "manu" guard let myName = name else { print("empty name - can't proceed") return } print(myName) “manu”
46. var myName : String! myName = “manu” print(myName) “manu”
47. One more thing...
49. This is the end ...
51. Think about Code changes because of no yet fixed ABI Swift version tied to Xcode version Swift based frameworks / libraries Longer compilation / building time Getting used to the ”swifty way” Swift, YEY of NEY … ? Have fun with Short and descriptive syntax (if you use it) Type safety Strong compiler time validation … definitively YEY!
54. Merci :) Manu Rink Technical Evangelist marink@microsoft.com @codeprincess says
55. Sources All memes from https://openclipart.org Rage face from http://knowyourmeme.com/ Not bad meme from http://nibler.ru/uploads/users/4233/2012-01- 31/%D0%BE%D0%B1%D0%BC%D0%B0%D0%BD%D1%83%D1%82%D1%8C- _83631761.jpg Taylor Swift article from https://mobilebusinessinsights.com/2016/10/more-than-a- blank-space-what-swift-design-has-in-common-with-taylor-swift/ Taylor Swift memes from http://giphy.com All Swift types scribble graphics © Manuela Rink