Playground in Swift 3

Cocoa Programming for OS X (5th Edition) 2. Swift Types
1

Original reverse() is renamed as reversed()

var countingUp = ["one", "two", "three"]

//let countingDown = countingUp.reverse()   // Swift 1
let countingDown = countingUp.reversed()    // ["three", "two", "one"]

Another name change from enumerate() to enumerated()

//for (i, string) in enumerate(countingUp) {    // Swift 1
//for (i, string) in countingUp.enumerate() {   // Swift 2
for (i, string) in countingUp.enumerated() {
  print("\(i): \(string)")
}