A swift introduction to Swift

A swift introduction to
Giordano Scalzo
Closure Busker

iOS Dev
geek
giordano.scalzo@gmail.com

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

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")
}

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
for item in list {
return true
}
}
return false
}
return number < 10
}
var numbers = [20, 19, 7, 12]
hasAnyMatches(numbers, { num in num < 10})

for item in list {
return true
}
}
return false
}
return number < 10
}
var numbers = [20, 19, 7, 12]
hasAnyMatches(numbers) { num in num < 10}
anonymous function

for item in list {
return true
}
}
return false
}
return number < 10
}
var numbers = [20, 19, 7, 12]
hasAnyMatches(numbers) { $0 < 10}
anonymous function

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()

init(sideLength len: Double, name: String) {
self.sideLength = len
numberOfSides = 4
}
}
(sideLength)."
}
}
!
let test = Square(sideLength: 5.2, name: "my test square")
test.area()

init(_ sideLength: Double, _ name: String) {
self.sideLength = sideLength
numberOfSides = 4
}
}
(sideLength)."
}
}
!
let test = Square(5.2, "my test square")
test.area()

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
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
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
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

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...

For me (imvho) the most useful new
features are enumerations and pattern
matching

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!")
}
}
}
}
}
}

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

A swift introduction to Swift

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