ArraySubscriptExamples.swift

//An array of strings that specify their indices
let strings: Array = ["zero", "one"]

//Set to default "two"
let one = strings[2, default: "two"]
//Set to default nil
let twoNil = strings[2, default: nil]

//Optionally binding the value from a valid index
if let one = strings[1, default: nil] {
  print(one) //prints "one"
}

//Optionally binding the value from an invalid index
if let twoNilUnwrapped = strings[2, default: nil] {
  //Never runs because nil is returned
  print(twoNilUnwrapped) 
 }