swift: apple's new programming language for ios and os x

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This presentation: http://s.sashag.net/sa-swift

SwiftApple’s New Programming Language

Sasha GoldshteinCTO, Sela Group

blog.sashag.net @goldshtn

Apple WWDC Announcements

• iOS 8 and OS X Yosemite

• Xcode 6

• Swift

Minus Bazillion Points

“Every feature starts out in the hole by 100 points, which means that it has to have a significant net positive effect on the overall package for it to make it into the language.”

– Eric Gunnerson, C# compiler team

If a language feature starts at -100 points, where does a new language start?!

Objective-C Popularity

• Objective-C owes all its popularity to the meteoric rise of the iPhone

App Store introduced

What’s Wrong with Objective-CExhibit One

// Ignore the horrible syntax for a second.// But here's the charmer:// 1) if 'str' is null, we return NSNotFound (232-1)// 2) if 'arr' is null, we return 0

+ (NSUInteger)indexOfString:(NSString *)str inArray:(NSArray *)arr{ return [arr indexOfObject:str];}

What’s Wrong with Objective-CExhibit Two

// This compiles and crashes at runtime with:// "-[__NSArrayI addObject:]: unrecognized selector// sent to instance 0x7a3141c0"

NSMutableArray *array = [NSArray array];[array addObject:@"hello"];

What’s Wrong with Objective-CExhibit Three

NSMutableArray *array = [NSMutableArray array];[array addObject:@"hello"];[array addObject:@17]; // This compiles just fineNSString *string = array[1]; // Yes, the "17"// This works and prints 17NSLog(@"%@", string);// But this crashesNSLog(@"%@", [string stringByAppendingString:@"hmm"]);

Swift Language Principles

• Clean and modern

• Type-safe and generic

• Extensible

• Functional

• Productive

• Compiled to native

• Seamlessly interops with Objective-C

Why Not an Existing Language?

• Good philosophical question

• If you want some more philosophy:http://s.sashag.net/why-swift

We will now review some of the interesting language decisions, which make Swift different from mainstream languages

Variables and Constants

let size = 42let name = "Dave"

var address = "14 Franklin Way"address = "16 Calgary Drive"

var city: Stringcity = "London"

var pi: Double = 3.14

Strings and Arrays

var fullAddress = city + " " + addressprintln("\(name)'s at \(city.capitalizedString)")

var customers = ["Dave", "Kate", "Jack"]var addresses = [String]()addresses += fullAddress

if customers[2].hasPrefix("Ja") { customers.removeAtIndex(2)}

Dictionaries

var orderSummary = [ "Dave": 11000, "Kate": 14000, "Jack": 13500]orderSummary["Kate"] = 17500

for (customer, orders) in orderSummary { println("\(customer) -> \(orders)")}

“I call it my billion-dollar mistake. It was the invention of the null reference in 1965. […] I couldn't resist the temptation to put in a null reference, simply because it was so easy to implement. This has led to innumerable errors, vulnerabilities, and system crashes, which have probably caused a billion dollars of pain and damage in the last forty years.”

– Sir Charles Antony Richard Hoare, 2009

Optional Types

var myName: StringmyName = nil // Does not compile!

var jeffsOrders: Int?jeffsOrders = orderSummary["Jeff”]if jeffsOrders { let orders: Int = jeffsOrders!}

var customerName: String? = getCustomer()println("name: \(customerName?.uppercaseString)")

Pattern Matching

switch milesFlown["Jeff"]! {case 0..<25000: println("Jeff is a Premier member")case 25000..<50000: println("Jeff is a Silver member")case 50000..<75000: println("Jeff is a Gold member")case 75000..<100000: println("Jeff is a Platinum member")default: println("Jeff is an Elite member")}

Pattern Matching

switch reservation.fareClass {case "F", "A", "J", "C": milesBonus = 2.5 // business/firstcase "Y", "B": milesBonus = 2.0 // full-fare economycase "M", "H": milesBonus = 1.5 // top-tier discount economycase let fc where fc.hasPrefix("Z"): milesBonus = 0 // upgrades don't earn milesdefault: milesBonus = 1.0}

Functions and Tuples

func square(x: Int) -> Int { return x * x }

func powers(x: Int) -> (Int, Int, Int) { return (x, x*x, x*x*x)}

// The first tuple element is ignoredlet (_, square, cube) = powers(42)

Closures

func countIf(arr: [Int], pred: (Int) -> Bool) { var count = 0 for n in arr { if pred(n) { ++count } } return count}countIf([1, 2, 3, 4], { n in n % 2 == 0 })

var squares = [17, 3, 11, 5, 7].map({ x in x * x })sort(&squares, { a, b in a > b })sort(&squares) { a, b in a > b }sort(&squares) { $0 > $1 }

DEMOSwift REPL

Classes

class FrequentFlier { let name: String var miles: Double = 0 init(name: String) { self.name = name } func addMileage(fareClass: String, dist: Int) { miles += bonus(fareClass) * Double(dist) }}

Custom Properties and Observers

class MileageStatus { var miles: Double = 0.0 { willSet { assert(newValue >= miles) // can't decrease one's mileage } }

var status: String { get { switch miles { /* ... */ } } }}

Smart Enums

enum MemberLevel { case Silver case Gold case Platinum func milesRequired() -> Int { switch self { case .Silver: return 25000 case .Gold: return 50000 case .Platinum: return 75000 } }}

Stateful Enums

enum HttpResponse { case Success(body: String) case Error(description: String, statusCode: Int)}switch fakeHttpRequest("example.org") {case let .Error(desc, status) where status >= 500: println("internal server error: \(desc)")case let .Error(desc, status): println("error \(status) = \(desc)")case .Success(let body): println("success, body = \(body)")}

Extensions

extension Int { var absoluteValue: Int { get { return abs(self) } } func times(action: () -> Void) { for _ in 1...self { action() } }}5.times { println("hello") }println((-5).absoluteValue)

Generics

class Queue<T> { var items = [T]() var depth: Int { get { return items.count } } func enqueue(item: T) { items.append(item) } func dequeue() -> T { return items.removeAtIndex(0) }}

Operators

struct Complex { var r: Double, i: Double func add(z: Complex) -> Complex { return Complex(r: r+z.r, i: i+z.i) } }

@infix func +(z1: Complex, z2: Complex) -> Complex { return z1.add(z2)}

Custom Operators (Oh My!)

operator prefix &*^%!~ {}@prefix func &*^%!~(s: String) -> String { return s.uppercaseString}

operator infix ^^ { associativity left }@infix func ^^(a: Double, b: Double) -> Double { return pow(a, b)}

println(&*^%!~"hello") // prints "HELLO"println(2.0^^4.0) // prints 8.0

Swift and Objective-C

DEMOBuilding an iOS app with Swift

Wrapping Up

• Most iOS developers are extremely excited about Swift

• Swift has a much smoother learning curve and fixes many Objective-C mistakes

• For the foreseeable future though, we will still use both languages

Thank You!

Sasha Goldshtein

blog.sashag.net

@goldshtn

s.sashag.net/sa-swift

swift: apple's new programming language for ios and os x

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