A swift introduction to Swift

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giordano-scalzo-scalzo
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Description
A quick introduction to Swift, the new language Apple introduced in WWDC14 to create apps for iOS and OSX
Text
  • A swift introduction to Giordano Scalzo Closure Busker
  • iOS Dev geek giordano.scalzo@gmail.com
  • with different reactions
  • but also
  • From
  • To
  • What does Swift look like?
  • SHOW ME THE CODE!!!!!
  • let individualScores = [75, 43, 103, 87, 12] var teamScore = 0 for score in individualScores { if score > 50 { teamScore += 3 } else { teamScore += 1 } } teamScore
  • ;
  • ;
  • var optionalName: String? = "John Appleseed" var greeting = "Hello!" ! if optionalName { greeting = "Hello, (optionalName!)" } Optional
  • var optionalName: String? = "John Appleseed" var greeting = "Hello!" ! if let name = optionalName { greeting = "Hello, (name)" } Optional
  • if let upper = john.residence?.address?.buildingIdentifier()?.uppercaseString { println("John's uppercase building identifier is (upper).") } else { println("I can't find John's address") } Optional Chaining
  • Playground
  • Switch on steroids
  • let vegetable = "red pepper" switch vegetable { case "celery": let vegetableComment = "Add raisins." case "cucumber", "watercress": let vegetableComment = "sandwich." case let x where x.hasSuffix("pepper"): let vegetableComment = "Is it a spicy (x)?" default: let vegetableComment = "Soup." }
  • let somePoint = (1, 1) switch somePoint { case (0, 0): println("(0, 0) is at the origin") case (_, 0): println("((somePoint.0), 0) is on the x-axis") case (0, _): println("(0, (somePoint.1)) is on the y-axis") case (-2...2, -2...2): println("((somePoint.0), (somePoint.1)) is inside the box") default: println("((somePoint.0), (somePoint.1)) is outside of the box") }
  • Functions and closures
  • func greet(name: String, #day: String) -> String { return "Hello (name), today is (day)." } greet("Bob", day: "Wednesday") Named Parameters
  • func greet(name: String, day: String) -> String { return "Hello (name), today is (day)." } greet("Bob", "Wednesday") Named Parameters Optional
  • Multiple result using tuples func getGasPrices()->(Double, Double, Double) { return (3.59, 3.69, 3.79) } let (min, avg, max) = getGasPrices() println("min is (min), max is (max)")
  • Multiple result using tuples func getGasPrices()->(Double, Double, Double) { return (3.59, 3.69, 3.79) } let gasPrices = getGasPrices() println("min is (gasPrices.0), max is (gasPrices.2)")
  • Functions are first class type
  • func makeIncrementer() -> (Int -> Int) { func addOne(number: Int) -> Int { return 1 + number } return addOne } var increment = makeIncrementer() increment(7) A function can be a return value
  • or a function parameter func hasAnyMatches(list: Int[], condition: Int -> Bool) -> Bool { for item in list { if condition(item) { return true } } return false } func lessThanTen(number: Int) -> Bool { return number < 10 } var numbers = [20, 19, 7, 12] hasAnyMatches(numbers, lessThanTen)
  • anonymous function func hasAnyMatches(list: Int[], condition: Int -> Bool) -> Bool { for item in list { if condition(item) { return true } } return false } func lessThanTen(number: Int) -> Bool { return number < 10 } var numbers = [20, 19, 7, 12] hasAnyMatches(numbers, { num in num < 10})
  • func hasAnyMatches(list: Int[], condition: Int -> Bool) -> Bool { for item in list { if condition(item) { return true } } return false } func lessThanTen(number: Int) -> Bool { return number < 10 } var numbers = [20, 19, 7, 12] hasAnyMatches(numbers) { num in num < 10} anonymous function
  • func hasAnyMatches(list: Int[], condition: Int -> Bool) -> Bool { for item in list { if condition(item) { return true } } return false } func lessThanTen(number: Int) -> Bool { return number < 10 } var numbers = [20, 19, 7, 12] hasAnyMatches(numbers) { $0 < 10} anonymous function
  • Where are the classes?
  • class NamedShape { var numberOfSides: Int = 0 var name: String init(name: String) { self.name = name } func simpleDescription() -> String { return "A shape with (numberOfSides) sides." } }
  • class Square: NamedShape { var sideLength: Double init(sideLength: Double, name: String) { self.sideLength = sideLength super.init(name: name) numberOfSides = 4 } func area() -> Double { return sideLength * sideLength } override func simpleDescription() -> String { return "A square with sides of length (sideLength)." } } ! let test = Square(sideLength: 5.2, name: "my test square") test.area() test.simpleDescription()
  • class Square: NamedShape { var sideLength: Double init(sideLength len: Double, name: String) { self.sideLength = len super.init(name: name) numberOfSides = 4 } func area() -> Double { return sideLength * sideLength } override func simpleDescription() -> String { return "A square with sides of length (sideLength)." } } ! let test = Square(sideLength: 5.2, name: "my test square") test.area() test.simpleDescription()
  • class Square: NamedShape { var sideLength: Double init(_ sideLength: Double, _ name: String) { self.sideLength = sideLength super.init(name: name) numberOfSides = 4 } func area() -> Double { return sideLength * sideLength } override func simpleDescription() -> String { return "A square with sides of length (sideLength)." } } ! let test = Square(5.2, "my test square") test.area() test.simpleDescription()
  • class EquilateralTriangle: NamedShape { var sideLength: Double = 0.0 ... var perimeter: Double { get { return 3.0 * sideLength } set { sideLength = newValue / 3.0 } } ... } calculated properties
  • class TriangleAndSquare { var triangle: EquilateralTriangle { willSet { square.sideLength = newValue.sideLength } } var square: Square { willSet { triangle.sideLength = newValue.sideLength } } } observable properties
  • struct Card { var rank: Rank var suit: Suit func simpleDescription() -> String { return "The (rank.simpleDescription()) of (suit.simpleDescription())" } } let threeOfSpades = Card(rank: Card.Three, suit: Card.Spades) let threeOfSpadesDescription = threeOfSpades.simpleDescription() Structs
  • struct Card { var rank: Rank var suit: Suit func simpleDescription() -> String { return "The (rank.simpleDescription()) of (suit.simpleDescription())" } } let threeOfSpades = Card(rank: .Three, suit: .Spades) let threeOfSpadesDescription = threeOfSpades.simpleDescription() Structs
  • like classes, but passed by value...in a smarter way
  • classes are always passed by reference structs are passed by reference, but automatically copied when mutated
  • Struct are used as ValueTypes, data components manipulated by classes
  • https://www.destroyallsoftware.com/talks/boundaries
  • enum Rank: Int { case Ace = 1 case Two, Three, Four, Five, Six, Seven, Eight, Nine, Ten case Jack, Queen, King func simpleDescription() -> String { switch self { case .Ace: return "ace" case .Jack: return "jack" case .Queen: return "queen" case .King: return "king" default: return String(self.toRaw()) } } } Enumerations on steroids
  • enum ServerResponse { case Result(String, String) case Error(String) } Enumerations with a value associated
  • Enumerations with a value associated let success = ServerResponse.Result("6:00 am", "8:09 pm") let failure = ServerResponse.Error("Out of cheese.")
  • Pattern matching to extract associated values switch result { case let .Result(sunrise, sunset): let serverResponse = "Sunrise is at (sunrise) and sunset is at (sunset)." case let .Error(error): let serverResponse = "Failure... (error)" }
  • protocol ExampleProtocol { var simpleDescription: String { get } mutating func adjust() } Protocols... like Interface in Java or... protocols in Objective-C
  • extension Int: ExampleProtocol { var simpleDescription: String { return "The number (self)" } mutating func adjust() { self += 42 } } 7.simpleDescription extensions... like categories in Objective-C
  • Generics
  • func repeatString(item: String, times: Int) -> String[] { var result = String[]() for i in 0..times { result += item } return result } repeatString("knock", 4)
  • ! func repeatInt(item: Int, times: Int) -> Int[] { var result = Int[]() for i in 0..times { result += item } return result } repeatInt(42, 4)
  • func repeat<T>(item: T, times: Int) -> T[] { var result = T[]() for i in 0..times { result += item } return result } repeat("knock", 4) repeat(42, 3)
  • Operator overload @infix func +(t1: Int, t2: Int) -> Int{ return 3 } ! @prefix func +(t1: Int) -> Int{ return 5 } ! var a = 20 var b = 111 ! a + b // 3 a - +b // 15
  • But the most important feature, the only one that you need to learn is...
  • Emoji!!!
  • For me (imvho) the most useful new features are enumerations and pattern matching
  • Unit Test support
  • XCTest class RpnCalculatorKataTests: XCTestCase { override func setUp() { super.setUp() } override func tearDown() { super.tearDown() } func testExample() { XCTAssert(true, "Pass") } func testPerformanceExample() { self.measureBlock() { } } }
  • Quick class PersonSpec: QuickSpec { override class func exampleGroups() { describe("Person") { var person: Person? beforeEach { person = Person() } describe("greeting") { context("when the person is unhappy") { beforeEach { person!.isHappy = false } it("is lukewarm") { expect(person!.greeting).to.equal("Oh, hi.") expect(person!.greeting).notTo.equal("Hello!") } } } } } }
  • And now...
  • Let's code
  • a Rpn Calculator
  • enum Key : String { case One = "1" //... case Enter = "enter" case Plus = "+" case Minus = "-" } ! protocol RpnCalculator { var display : String[] { get } func press(key: Key) } https://github.com/gscalzo/RpnCalculatorKata
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