takasek

protocol OptionalType {
    associatedtype Wrapped
    var optional: Wrapped? { get }
}

extension Optional : OptionalType {
    var optional: Wrapped? { return self }
}

extension CollectionType where Generator.Element: OptionalType {

takasek

// 整数計算で桁あふれが起こると実行時エラーになる
UInt8(254) + 1 // 255
//UInt8(255) + 1 // error: arithmetic operation '255 + 1' (on type 'UInt8') results in an overflow

// static func IntegerArithmeticType.xxxWithOverflowは、桁あふれの可能性のある計算で使える
UInt8.addWithOverflow(254, 1) // (.0 255, .1 false)
UInt8.addWithOverflow(255, 1) // (.0 0, .1 true)

takasek

// Doubleは実はゼロ除算可能(infが返る)
10/0.0 // inf

// Intではゼロ除算すると実行時エラー
//10/0 // error: division by zero

// IntegerArithmeticType.divideWithOverflowを使っても、ゼロ除算での実行時エラーは防げない
//UInt8.divideWithOverflow(254, 0) // error: division by zero

takasek

extension Bool {
    mutating func toggle() {
        self = !self
    }
}

var bool = true // true
bool.toggle() // false

let immutableBool = true

takasek

// UIControl
button.on(.TouchDown) {
    $0.backgroundColor = UIColor.redColor()
}
button.on(.TouchUpOutside) {
    $0.backgroundColor = UIColor.whiteColor()
}
// UIButton
button.onTap {
    $0.enabled = false

takasek

struct Hoge<T> {
    let v: T
}

protocol P {}
extension String: P {}

let s = Hoge(v: "a")

let sp = s as? Hoge<P> // Cast from 'Hoge<String>' to unrelated type 'Hoge<P>' always fails

takasek

//cf. http://yannickloriot.com/2016/06/measurements-and-units-ios/

public struct Measurement<UnitType: Unit>: Comparable, Equatable {
  public init(value: Double, unit: UnitType)
}

public class Unit: NSObject, NSCopying {
  public init(symbol: String)
}

takasek

(label.text, button.selected, slider.value) = {
    () -> (text: String?, selected: Bool, value: Float) in
    switch condition {
    case .one:
        return (text: "1", selected: true, value: 0.1)
    case .two:
        return (text: 2, selected: false, value: 0.2)
        //error:
        //  cannot convert return expression of type 'Int' to return type 'String?'
    case .three:

takasek

(c: labelC.text, a: labelA.text, b: labelB.text) = {
    switch condition {
    case .one:
        return (a: "1", b: "11", c: "111")
    case .two:
        return (b: "22", c: "222", a: "2")
    case .three:
        return (a: "3", c: "333", b: "33")
    }
}()

takasek

func apply <A, B>(f : A -> B, a : A) -> B {
    return f(a)
}

func p(a a: Int, b: Int) {
    print("a: \(a)")
    print("b: \(b)")
}

let tuple: (b: Int, a: Int) = (b: 2, a: 1)