Swiftツアーをやることにします

チュートリアル大事

おはようございます。僕です。みなさんはチュートリアルとか説明書とかって読む方ですか？僕はよまないです。読まないで動かします。読まないで動かすので大体途中で詰みます。

Swift公式
https://swift.org/

てなわけでSwiftとかLL言語みたいなノリで覚えられるでしょとか思って動かしてたら意外と詰んだので、初心に戻ってSwiftツアーを読み直すことにしました。

A Swift Tour
ちょうどここですね。ここをやっていきます。あ、バージョンは4.2で確認していきます。まあ、写経記事になりそうだけど、何かあったら補足とか愚痴とかグダグダ書き入れていきますんでそれで勘弁。

print("Hello, world!")
// Prints "Hello, world!"

出力

Hello, world!

まずは、世界と挨拶です。特に問題点はありません。

var myVariable = 42
myVariable = 50
let myConstant = 42

let implicitInteger = 70
let implicitDouble = 70.0
let explicitDouble: Double = 70
let explicitFloat: Float = 4

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

varは変数、letは定数だそうです。String外すとerror: binary operator '+' cannot be applied to operands of type 'String' and 'Int'みたいな感じで型の不一致で怒られます。

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

代入してみる。\( )使うとこっちは文字列と認識してくれるっぽい。

let apples = 3
let oranges = 5
let quotation = """
Even though there's whitespace to the left,
the actual lines aren't indented.
Except for this line.
Double quotes (") can appear without being escaped.

I still have \(apples + oranges) pieces of fruit.
    """

ヒアドキュメント的な書き方。括弧の中身がないとerror: use of unresolved identifier '***'って怒られます。

var shoppingList = ["catfish", "water", "tulips"]
shoppingList[1] = "bottle of water"

var occupations = [
    "Malcolm": "Captain",
    "Kaylee": "Mechanic",
]
occupations["Jayne"] = "Public Relations"

shoppingList.append("blue paint")
print(shoppingList)

出力

["catfish", "bottle of water", "tulips", "blue paint"]

配列的なやつ。辞書も混じってるけどまあ細かいことはいいんだよ。

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

空配列はこのように作るっぽいです。

let individualScores = [75, 43, 103, 87, 12]
var teamScore = 0
for score in individualScores {
    if score > 50 {
        teamScore += 3
    } else {
        teamScore += 1
    }
}
print(teamScore) // Prints "11"

普通のfor-in文でのループです。昔ながらの"for"文は存在しないらしいよ。

var optionalString: String? = "Hello"
print(optionalString == nil) // Prints "false"

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

いわゆるif文です。nilが偽判定になるそうです。そしてしれっと出てくる末尾「？」。こいつは一体何者なのか………*1。

let nickName: String? = nil
let fullName: String = "John Appleseed"
let informalGreeting = "Hi \(nickName ?? fullName)" // "Hi John Appleseed"

??使うとnil専用if文みたいに使えるそうです。

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

Switch文の書き方です。default:がないとerror: switch must be exhaustiveとか言われて怒られます。

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
        }
    }
}
print(largest)　// Prints "25"

辞書でのforループの書き方みたいなやつ。

var n = 2
while n < 100 {
    n *= 2
}
print(n) // Prints "128"

var m = 2
repeat {
    m *= 2
} while m < 100
print(m) // Prints "128"

Whileループの書き方。特に語ることはないと思われ。

var total = 0
for i in 0..<4 {
    total += i
}
print(total) // Prints "6"

for-inループは上のようにもかけるようです。エモい……。

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

関数編です。入出力の型が割とはっきりしている感じになります。

func greet(_ person: String, on day: String) -> String {
    return "Hello \(person), today is \(day)."
}
greet("John", on: "Wednesday")

”_”を使うことで引数のラベルperson:を省略できるとのことです。

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(scores: [5, 3, 100, 3, 9])
print(statistics.sum) // Prints "120"
print(statistics.2) // Prints "120"

複数返り値の出し方。個人的に番号指定はよみづらく感じる……。

func returnFifteen() -> Int {
    var y = 10
    func add() {
        y += 5
    }
    add()
    return y // 15
}
returnFifteen()

関数の中で関数を使ってみる。

func makeIncrementer() -> ((Int) -> Int) {
    func addOne(number: Int) -> Int {
        return 1 + number
    }
    return addOne
}
var increment = makeIncrementer()
increment(7) // 8

関数の入れ子構造について。

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(list: numbers, condition: lessThanTen) // true

引数に関数をねじ込んでみる。

var numbers = [20, 19, 7, 12]
numbers.map({ (number: Int) -> Int in
    let result = 3 * number
    return result // [60, 57, 21, 36]
})

mapの使い方（雑解釈）。なんでも三倍にしてくれるやつだよ。

var numbers = [20, 19, 7, 12]
let mappedNumbers = numbers.map({ number in 3 * number })
print(mappedNumbers) // Prints "[60, 57, 21, 36]"

let sortedNumbers = numbers.sorted { $0 > $1 }
print(sortedNumbers) // Prints "[20, 19, 12, 7]"

mapは非破壊的らしい。

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

var shape = Shape()
shape.numberOfSides = 7
var shapeDescription = shape.simpleDescription() // A shape with 7 sides."

クラス編に突入です。呼び出して使わないとプレイグランド上では存在を認識してくれない。

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

var shape = NamedShape(name: "heptagon")
shape.numberOfSides = 7
var shapeDescription = shape.simpleDescription() // "A shape with 7 sides."

初期化の書き方。

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() // 27.04
test.simpleDescription() // "A square with sides of length 5.2."

継承とかオーバーライドとか色々と……。

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 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")
print(triangle.perimeter) // Prints "9.3"
triangle.perimeter = 9.9
print(triangle.sideLength) // Prints "3.3000000000000003"

コンピューテッド・プロパティ、ゲットアンドセットの話（getterとsetter）。意図しない変更に対して効果があるらしいのだが、僕はそういう恩恵を感じる大規模なものを作ったことがないのでよくわからない。

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)."
    }
}
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)."
    }
}
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")
print(triangleAndSquare.square.sideLength) // Prints "10.0"
print(triangleAndSquare.triangle.sideLength) // Prints "10.0"
triangleAndSquare.square = Square(sideLength: 50, name: "larger square")
print(triangleAndSquare.triangle.sideLength)  // Prints "50.0"

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

さらに拡張してみる。コードが長くなってしまったけど見るべきところは最後の方の行にある?で、nilをどう扱っているのかとかです。

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 // 1

Enum編に突入。

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() // hearts

Enum編。スーツ版。恥ずかしながらトランプのマークのことをスーツって言うのこれ見るまで知りませんでした。

enum ServerResponse {
    case result(String, String)
    case failure(String)
}

let success = ServerResponse.result("6:00 am", "8:09 pm")
let failure = ServerResponse.failure("Out of cheese.")

switch success {
case let .result(sunrise, sunset):
    print("Sunrise is at \(sunrise) and sunset is at \(sunset).")
case let .failure(message):
    print("Failure...  \(message)")
}
// Prints "Sunrise is at 6:00 am and sunset is at 8:09 pm."

要素に値を定義できるEnum編。

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)
        }
    }
}

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"
        }
    }
}

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() // "The 3 of spades"

構造体の話。

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 // "A simple structure (adjusted)"

プロトコルの話。おまえは一体……。他言語でいうインターフェース的役割らしい。よくわかんないけど、使うと気がきたら思い出すようにします。

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

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

プロトコルエクステンション。使いこなせるとクラスとはまた違った管理ができるようになるらしい。

enum PrinterError: Error {
    case outOfPaper
    case noToner
    case onFire
}

func send(job: Int, toPrinter printerName: String) throws -> String {
    if printerName == "Never Has Toner" {
        throw PrinterError.noToner
    }
    return "Job sent"
}

do {
    let printerResponse = try send(job: 1040, toPrinter: "Bi Sheng")
    print(printerResponse)
} catch {
    print(error)
}
// Prints "Job sent"

do {
    let printerResponse = try send(job: 1440, toPrinter: "Gutenberg")
    print(printerResponse)
} catch PrinterError.onFire {
    print("I'll just put this over here, with the rest of the fire.")
} catch let printerError as PrinterError {
    print("Printer error: \(printerError).")
} catch {
    print(error)
}
// Prints "Job sent"

let printerSuccess = try? send(job: 1884, toPrinter: "Mergenthaler")
let printerFailure = try? send(job: 1885, toPrinter: "Never Has Toner")

エラーハンドリング。do-catch構文。

var fridgeIsOpen = false
let fridgeContent = ["milk", "eggs", "leftovers"]

func fridgeContains(_ food: String) -> Bool {
    fridgeIsOpen = true
    defer {
        fridgeIsOpen = false
    }
    
    let result = fridgeContent.contains(food)
    return result
}
fridgeContains("banana")
print(fridgeIsOpen) // Prints "false"

deferの使い方。エラーだろうとなにしようが絶対実行したいマン処理らしい。へー。

func makeArray<Item>(repeating item: Item, numberOfTimes: Int) -> [Item] {
    var result = [Item]()
    for _ in 0..<numberOfTimes {
        result.append(item)
    }
    return result
}
makeArray(repeating: "knock", numberOfTimes: 4) // ["knock", "knock", "knock", "knock"]

ジェネリクス編。

// Reimplement the Swift standard library's optional type
enum OptionalValue<Wrapped> {
    case none
    case some(Wrapped)
}
var possibleInteger: OptionalValue<Int> = .none // none
possibleInteger = .some(100) // some(100)

クラス、Enum、構造だけでなくいろんなものに使える（雑訳）。

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

whereを使って制約をつけてみる。

といった感じに使えるそうです。やってみようコーナーとかが合間合間に挟まっていたりしたけど、それは気が向いたら解いたりしていこうと思います。まだ使っててエラーぼこぼこと出すので、まずは慣れることからはじめていきたい。

*1:変数にはnilを代入することができるようにしたものです