String to number
var text: String = "111"
var number: Int? = Int(text)
let text: String = "111"
var n: Int = (text as NSString).integerValue
Number to String
let number: Float = 123.5
var string: String = "\(number)"
var number: Float = 123.5
var string = String(number)
Convert between numbers
var doubleNumber = 1.8
var intNumber = 0
intNumber = Int(doubleNumber)