今日は酒を飲んで気持ちがいい
struct TimesTable { let multiplier: Int subscript(index: Int) -> Int { return multiplier * index } } let threeTimesTable = TimesTable(multiplier: 3) print("six times three is \(threeTimesTable[6])") struct Some { subscript(table: TimesTable) -> Int { return table.multiplier } } Some()[threeTimesTable]
subscriptを初めて実装した．勝手にIntを使うものだと思ってたけど何でもいいらしい．
最近何にもモチベがわかなくて良くない．遅めの５月病というか中だるみ感がすごい．
struct LevelTracker { static var highestUnlockedLevel = 1 var currentLevel = 1 static func unlock(_ level: Int) { if level > highestUnlockedLevel { highestUnlockedLevel = level } } static func isUnlocked(_ level: Int) -> Bool { return level <= highestUnlockedLevel } @discardableResult mutating func advance(to level: Int) -> Bool { if LevelTracker.isUnlocked(level) { currentLevel = level return true } else { return false } } } class Player { var tracker = LevelTracker() let playerName: String func complete(level: Int) { LevelTracker.unlock(level + 1) tracker.advance(to: level + 1) } init(name: String) { playerName = name } } var player = Player(name: "Argyrios") player.complete(level: 1) print("highest unlocked level is now \(LevelTracker.highestUnlockedLevel)") // Prints "highest unlocked level is now 2" player = Player(name: "Beto") if player.tracker.advance(to: 6) { print("player is now on level 6") } else { print("level 6 hasn't yet been unlocked") } // Prints "level 6 hasn't yet been unlocked"
@discardableResult初めて使った．Methodsの章は今日で終わりだがだいたい知っていた気がする．
struct Point { var x = 0.0, y = 0.0 mutating func moveBy(x deltaX: Double, y deltaY: Double) { x += deltaX y += deltaY } } var somePoint = Point(x: 1.0, y: 1.0) somePoint.moveBy(x: 2.0, y: 3.0) print("The point is now at (\(somePoint.x), \(somePoint.y))") // => The point is now at (3.0, 4.0)
:pear:
ひぐらしのなく頃にの「頃」は夏なのか夕方なのか気になった．
class SomeClass { static var storedTypeProperty = "Some value." // class var overrideableStoredTypeProperty = "Some value." static var computedTypeProperty: Int { return 27 } class var overrideableComputedTypeProperty: Int { return 107 } } class SubClass: SomeClass { override static var overrideableComputedTypeProperty: Int { 2 } } class SubSubClass: SubClass { // SubClassでstatic varとなっているのでこれはできない // override static var overrideableComputedTypeProperty: Int { // 2 // } } print(SubClass.overrideableComputedTypeProperty) // => 2
classの中のtype propertyのうちcomputed propertyはstaticではなくclassを使うことでサブクラスでoverrideすることができる．
ご飯ができたので雑
@propertyWrapper struct SmallNumber { private var number = 0 var projectedValue = false var wrappedValue: Int { get { return number } set { if newValue > 12 { number = 12 projectedValue = true } else { number = newValue projectedValue = false } } } } enum Size { case small, large } struct SizedRectangle { @SmallNumber var height: Int @SmallNumber var width: Int mutating func resize(to size: Size) -> Bool { switch size { case .small: height = 10 width = 20 case .large: height = 100 width = 100 } return $height || $width } } var sized = SizedRectangle() print(sized.resize(to: .large), sized.$width, sized.$height) print(sized.resize(to: .small), sized.$width, sized.$height) // => true true true // => true true false
property wrapperはprojected valueを定義することで追加の機能を提供できる．上のコードの$で始まるやつ．SwiftUIでやたら便利なやつの意味がわかった．これどっちが先なんだろう．
アマプラでカイジを見ていたら忘れるところだった
@propertyWrapper struct TwelveOrLess { private var number = 0 var wrappedValue: Int { get { return number } set { number = min(newValue, 12) } } } struct SmallRectangle { @TwelveOrLess var height: Int @TwelveOrLess var width: Int } var rectangle = SmallRectangle() print(rectangle.height) // Prints "0" rectangle.height = 10 print(rectangle.height) // Prints "10" rectangle.height = 24 print(rectangle.height) // Prints "12" @propertyWrapper struct SmallNumber { private var maximum: Int private var number: Int var wrappedValue: Int { get { return number } set { number = min(newValue, maximum) } } init() { maximum = 12 number = 0 } init(wrappedValue: Int) { maximum = 12 number = min(wrappedValue, maximum) } init(wrappedValue: Int, maximum: Int) { self.maximum = maximum number = min(wrappedValue, maximum) } } struct NarrowRectangle { @SmallNumber(wrappedValue: 2, maximum: 5) var height: Int @SmallNumber(wrappedValue: 3, maximum: 4) var width: Int } var narrowRectangle = NarrowRectangle() print(narrowRectangle.height, narrowRectangle.width) // Prints "2 3" narrowRectangle.height = 100 narrowRectangle.width = 100 print(narrowRectangle.height, narrowRectangle.width) // Prints "5 4"
property wrapperが何なのか初めて知った．今はそんなにSwiftUIを書いていないのでおまじない程度に思っていたがなるほどという感じ．これでいろいろあるproperty wrapperの理解が楽になりそうだと思った．
今日はあまりに暇だったので明るいうちから書いている．
struct Cup { var content: String { willSet { print("willSet:", newValue) } didSet { print("didSet:", content) } } } func replace(_ newContet: String, from oldContent: inout String) { print("before pouring") oldContent = newContet print("after pouring") } func doNothing(_ content: inout String) {} var coffeeCup = Cup(content: "") print("call replace") replace("coffee", from: &(coffeeCup.content)) print("call doNothing") doNothing(&(coffeeCup.content)) // => call replace // => before pouring // => after pouring // => willSet: coffee // => didSet: coffee // => call doNothing // => willSet: coffee // => didSet: coffee
オブザーバを持つプロパティをin-outパラメータとして関数に渡すと，関数の最後でwillSetとdidSetが呼ばれる．これはin-outパラメータについては関数の最後で値が書き戻されるようになっているため．そうなっている理由はIn-Out Parametersに書かれていそうなのでその時が来たら読む．
If you pass a property that has observers to a function as an in-out parameter, the willSet and didSet observers are always called. This is because of the copy-in copy-out memory model for in-out parameters: The value is always written back to the property at the end of the function. For a detailed discussion of the behavior of in-out parameters, see In-Out Parameters. https://docs.swift.org/swift-book/LanguageGuide/Properties.html
