iOS Development with Swift

Appendix B. Swift syntax cheat sheets

Variables and constants

var aVariable = 0
let aConstant = 0

Data type annotations

var aString: String
var aBool: Bool
var aInt: Int
var aDouble: Double

Data type inference

var bString = "A String!"
var bBool = true
var bInt = 3
var bDouble = 3.0

Clarify data type

var cDouble: Double = 3

Convert data type

var dDouble = Double(3)

Property observers

var score = 0 {
  willSet {
    // Score will be updated
  }
  didSet {
    // Score was updated
  }
}

String interpolation

var message = "You scored\(score)"

Collections

Arrays

var emptyArray: [String] = []
var arrayOfInts = [3, 1, 2, 5]
arrayOfInts.append(4)

Dictionaries

var emptyDictionary: [String: String] = [:]
var dict = ["A": 1, "B": 2, "C": 3]
dict["D"] = 4