Cheat sheet

Just a bunch of short expressions in Swift.

let - readonly var

println(“ \() “)

? - Optional (can be not set)

enum Optional<T> { case None case Some(T) }

! - unwrap an optional (will crash if nil)

all properties have to be initialized and optionals are nil by default

getters and setters var name:type { get { } set { newValue } }

function signature shortcuts { (op1: Double, op2: Double) -> Double in return op1 * op2 } { (op1, op2) in op1 * op2 } { $0 * $1 }

array and map definition shortcuts Array<Double> - [Double] Dictionary<String, Double> - [String:Double]

Only classes are passed by reference (not structs)

Printable protocol: var description: String { get { } }

final prevents subclasses from using override

observe changes to a property willSet and didSet {newValue oldValue}

a property can be lazy

required & convenience init

init?(…) is a failable init

casting as or as? (will not crash) if let buttonItem = item as? UIButton { … }


set contentMode to properly redraw on view bounds change

add @IBDesignable to a view to allow Xcode to draw it and @IBInspectable to allow to modify properties from Xcode

use class in protocol to allow only classes (and not structs or enums) to implement it

?? if left side is nil use right side

fallthrough in switch means execute the next case

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