Manuela Rink Technical Evangelist @ The secret life of types in Swift 

What is Swift? 

Swift? 

Swift?!!? 

Swift!!! 

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! 

The Language 

v4 One-side ranges Comfortable encoding/decoding Multi-line string literals Improved key-value coding Strings as collections More powerful dictionaries Downwards compatibility* 

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 

IEEE Spectrum Language Ranking 2017 https://spectrum.ieee.org/computing/software/the-2017-top-programming-languages IEEE Spectrum Overall Readers 

IEEE Spectrum Language Ranking 2017 https://spectrum.ieee.org/computing/software/the-2017-top-programming-languages IEEE Spectrum Trending 

IEEE Spectrum Language Ranking 2017 https://spectrum.ieee.org/computing/software/the-2017-top-programming-languages IEEE Spectrum Mobile only 

? no fixed ABI with v3.0.1 update IDE – adapt code compatibility with Swift based frameworks 

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 

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! 

?! ! ? !!!!11eleven !? ? ? ! ? ? ! ? ! ? ! ? TYPES TYPES EVERYWHERE 

It’s all about types 

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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 

Obj-C Java java.lang.Object java.lang.Number java.lang.Integer conforms to: Serializable, Comparable 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 

Int Type in Swift http://swiftdoc.org/v3.1/ 

Float Dictionary http://swiftdoc.org/v3.1/ 

Dive into types 

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 

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Named Types 

Named types have ... names! 

… } 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! 

Int Type in Swift http://swiftdoc.org/v3.1/ 

Compound Types 

Compound types have … no names And that’s a good thing! 

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 

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 

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 

() It’s Void! public typealias Void = () let myAge : (Int) = (23) let myAge : Int = 23 (Type) == Type 

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 

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 

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)”) } } 

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: <) 

http://fuckingblocksyntax.com/ http://fuckingclosuresyntax.com/ 

the sugar on the top 

?! Don’t be afraid … it’s just Optionals public enum ImplicitlyUnwrappedOptional : 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: ()) } 

var myName : Optional myName = "manu” var theName = “manu” if myName != nil && theName != nil { print(myName) print(theName) } “Optional(“manu”)” “manu” 

var myName : String? = “manu” print(myName) print(myName!) if let name = myName { print(name) } “Optional(“manu”)” “manu” “manu” 

var name : String? = "manu" guard let myName = name else { print("empty name - can't proceed") return } print(myName) “manu” 

var myName : String! myName = “manu” print(myName) “manu” 

One more thing... 

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This is the end ... 

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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! 

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Merci :) Manu Rink Technical Evangelist [email protected] @codeprincess says 

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