a_swift_tour.md

Swiftツアー

println("Hello, world!")

変数

varは変数　letは定数

var myVariable = 42
myVariable = 50
let myConstant = 42

値型は必ずしも明示する必要はない

let implicitInteger = 70
let implicitDouble = 70.0
let explicitDouble: Double = 70

文字列は + で連結

let label = "The width is "
let width = 94
let widthLabel = label + String(width)

文字リテラルで変数・定数を簡単に含める事が可能

let apples = 3
let oranges = 5
let appleSummary = "I have \(apples) apples."
let fruitSummary = "I have \(apples + oranges) pieces of fruit."

配列と辞書

var shoppingList = ["catfish", "water", "tulips", "blue paint"]
shoppingList[1] = "bottle of water"
 
var occupations = [
    "Malcolm": "Captain",
    "Kaylee": "Mechanic",
]
occupations["Jayne"] = "Public Relations"

配列と辞書の初期化

let emptyArray = [String]()
let emptyDictionary = [String: Float]()

初期化の短い書き方

shoppingList = []
occupations = [:]

制御文

for ループ

let individualScores = [75, 43, 103, 87, 12]
var teamScore = 0
for score in individualScores {
    if score > 50 {
        teamScore += 3
    } else {
        teamScore += 1
    }
}
println(teamScore)

firstForLoop と secondForLoop は同じ意味のコード

var firstForLoop = 0
for i in 0..<4 {
    firstForLoop += i
}
println(firstForLoop)

var secondForLoop = 0
for var i = 0; i < 4; ++i {
    secondForLoop += i
}
println(secondForLoop)

オプショナル

var optionalString: String? = "Hello"
println(optionalString == nil)

条件分岐　if の条件指定で let を用いる nil チェックに変わる型安全な判定がswift流

var optionalName: String? = "John Appleseed"
var greeting = "Hello!"
if let name = optionalName {
    greeting = "Hello, \(name)"
}

条件分岐　switch

let vegetable = "red pepper"
switch vegetable {
case "celery":
    let vegetableComment = "Add some raisins and make ants on a log."
case "cucumber", "watercress":
    let vegetableComment = "That would make a good tea sandwich."
case let x where x.hasSuffix("pepper"):
    let vegetableComment = "Is it a spicy \(x)?"
default:
    let vegetableComment = the"Everything tastes good in soup."
}

辞書と配列による繰り返し

let interestingNumbers = [
    "Prime": [2, 3, 5, 7, 11, 13],
    "Fibonacci": [1, 1, 2, 3, 5, 8],
    "Square": [1, 4, 9, 16, 25],
]
var largest = 0
for (kind, numbers) in interestingNumbers {
    for number in numbers {
        if number > largest {
            largest = number
        }
    }
}
println(largest)

while ループ

var n = 2
while n < 100 {
    n = n * 2
}
println(n)
 
var m = 2
do {
    m = m * 2
} while m < 100
println(m)

関数とクロージャー

関数定義

func greet(name: String, day: String) -> String {
    return "Hello \(name), today is \(day)."
}
greet("Bob", "Tuesday")

クロージャー

func calculateStatistics(scores: [Int]) -> (min: Int, max: Int, sum: Int) {
    var min = scores[0]
    var max = scores[0]
    var sum = 0
    
    for score in scores {
        if score > max {
            max = score
        } else if score < min {
            min = score
        }
        sum += score
    }
    
    return (min, max, sum)
}
let statistics = calculateStatistics([5, 3, 100, 3, 9])
println(statistics.sum)
println(statistics.2)

可変長引数

func sumOf(numbers: Int...) -> Int {
    var sum = 0
    for number in numbers {
        sum += number
    }
    return sum
}
sumOf()
sumOf(42, 597, 12)

内部関数

func returnFifteen() -> Int {
    var y = 10
    func add() {
        y += 5
    }
    add()
    return y
}
returnFifteen()

返値が関数

func makeIncrementer() -> (Int -> Int) {
    func addOne(number: Int) -> Int {
        return 1 + number
    }
    return addOne
}
var increment = makeIncrementer()
increment(7)

引数が関数

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)

map関数のクロージャー

numbers.map({
    (number: Int) -> Int in
    let result = 3 * number
    return result
})

map関数のクロージャー　短い書き方

let mappedNumbers = numbers.map({ number in 3 * number })
println(mappedNumbers)

引数は$0,$1と表現できる

let sortedNumbers = sorted(numbers) { $0 > $1 }
println(sortedNumbers)

オブジェクトとクラス

クラス定義

class Shape {
    var numberOfSides = 0
    func simpleDescription() -> String {
        return "A shape with \(numberOfSides) sides."
    }
}

インスタンス化

var shape = Shape()
shape.numberOfSides = 7
var shapeDescription = shape.simpleDescription()

クラス定義　イニシャライザー

class NamedShape {
    var numberOfSides: Int = 0
    var name: String
    
    init(name: String) {
        self.name = name
    }
    
    func simpleDescription() -> String {
        return "A shape with \(numberOfSides) sides."
    }
}

クラス定義　継承、イニシャライザー追加、オーバーライド

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()

クラス定義　継承、プロパティの初期値、アクセッサー

class EquilateralTriangle: NamedShape {
    var sideLength: Double = 0.0
    
    init(sideLength: Double, name: String) {
        self.sideLength = sideLength
        super.init(name: name)
        numberOfSides = 3
    }
    
    var perimeter: Double {
        get {
            return 3.0 * sideLength
        }
        set {
            sideLength = newValue / 3.0
        }
    }
    
    override func simpleDescription() -> String {
        return "An equilateral triangle with sides of length \(sideLength)."
    }
}
var triangle = EquilateralTriangle(sideLength: 3.1, name: "a triangle")
println(triangle.perimeter)
triangle.perimeter = 9.9
println(triangle.sideLength)

クラス定義　プロパティオブザーバー

class TriangleAndSquare {
    var triangle: EquilateralTriangle {
        willSet {
            square.sideLength = newValue.sideLength
        }
    }
    var square: Square {
        willSet {
            triangle.sideLength = newValue.sideLength
        }
    }
    init(size: Double, name: String) {
        square = Square(sideLength: size, name: name)
        triangle = EquilateralTriangle(sideLength: size, name: name)
    }
}
var triangleAndSquare = TriangleAndSquare(size: 10, name: "another test shape")
println(triangleAndSquare.square.sideLength)
println(triangleAndSquare.triangle.sideLength)
triangleAndSquare.square = Square(sideLength: 50, name: "larger square")
println(triangleAndSquare.triangle.sideLength)

クラスメソッドの引数が名前を持つ例。引数名を持つ事で読解可能、呼び出しの書き方が自然な英語のように表現出来る。

class Counter {
    var count: Int = 0
    func incrementBy(amount: Int, numberOfTimes times: Int) {
        count += amount * times
    }
}
var counter = Counter()
counter.incrementBy(2, numberOfTimes: 7)

オプショナル値の場合、?マークでアンラップしつつメソッドやプロパティにアクセス可能。 nilの際はそのままnilが返る。

let optionalSquare: Square? = Square(sideLength: 2.5, name: "optional square")
let sideLength = optionalSquare?.sideLength

列挙型と構造体

列挙型　

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.rawValue)
        }
    }
}
let ace = Rank.Ace
let aceRawValue = ace.rawValue

if let convertedRank = Rank(rawValue: 3) {
    let threeDescription = convertedRank.simpleDescription()
}

enum Suit {
    case Spades, Hearts, Diamonds, Clubs
    func simpleDescription() -> String {
        switch self {
        case .Spades:
            return "spades"
        case .Hearts:
            return "hearts"
        case .Diamonds:
            return "diamonds"
        case .Clubs:
            return "clubs"
        }
    }
}
let hearts = Suit.Hearts
let heartsDescription = hearts.simpleDescription()

構造体

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()

列挙型のcaseは引数を持てる

enum ServerResponse {
    case Result(String, String)
    case Error(String)
}
 
let success = ServerResponse.Result("6:00 am", "8:09 pm")
let failure = ServerResponse.Error("Out of cheese.")
 
switch success {
case let .Result(sunrise, sunset):
    let serverResponse = "Sunrise is at \(sunrise) and sunset is at \(sunset)."
case let .Error(error):
    let serverResponse = "Failure...  \(error)"
}

プロトコルとエクステンション

プロトコル定義とその適用

protocol ExampleProtocol {
    var simpleDescription: String { get }
    mutating func adjust()
}

class SimpleClass: ExampleProtocol {
    var simpleDescription: String = "A very simple class."
    var anotherProperty: Int = 69105
    func adjust() {
        simpleDescription += "  Now 100% adjusted."
    }
}
var a = SimpleClass()
a.adjust()
let aDescription = a.simpleDescription
 
struct SimpleStructure: ExampleProtocol {
    var simpleDescription: String = "A simple structure"
    mutating func adjust() {
        simpleDescription += " (adjusted)"
    }
}
var b = SimpleStructure()
b.adjust()
let bDescription = b.simpleDescription

エクステンションで直接機能拡張が可能

extension Int: ExampleProtocol {
    var simpleDescription: String {
        return "The number \(self)"
    }
    mutating func adjust() {
        self += 42
    }
}
println(7.simpleDescription)

let protocolValue: ExampleProtocol = a
println(protocolValue.simpleDescription)
// println(protocolValue.anotherProperty)  // Uncomment to see the error

ジェネリクス

ジェネリクスによる抽象化で引数の型を限定しない

func repeat<Item>(item: Item, times: Int) -> [Item] {
    var result = [Item]()
    for i in 0..<times {
        result.append(item)
    }
    return result
}
repeat("knock", 4)

Swiftスタンダードライブラリーのオプショナル型を再実装

// Reimplement the Swift standard library's optional type
enum OptionalValue<T> {
    case None
    case Some(T)
}
var possibleInteger: OptionalValue<Int> = .None
possibleInteger = .Some(100)

whereは省略可能で <T where T: Equatable> を <T: Equatable> とできる

func anyCommonElements <T, U where T: SequenceType, U: SequenceType, T.Generator.Element: Equatable, T.Generator.Element == U.Generator.Element> (lhs: T, rhs: U) -> Bool {
    for lhsItem in lhs {
        for rhsItem in rhs {
            if lhsItem == rhsItem {
                return true
            }
        }
    }
    return false
}
anyCommonElements([1, 2, 3], [3])