Swift 5.4 references for busy coders


Optionals are variables that can have a value of nil (nothing). More specifically, Optional is a type that represents either a wrapped value of a specific type, or nil. For example, an optional String is a variable that holds either a wrapped String or nil.

An optional is denoted with a ? or a !.

Simple example

func divide(x: Int, y: Int) -> Int? {
  if y == 0 {
    return nil
  } else {
    return x / y  

print(divide(x: 16, y: 2))
// Prints "Optional(8)"

print(divide(x: 16, y: 0))
// Prints "nil"