// *** before: ***
enum DirectionOld {
    case north, south, east, west

    // the list was kept by hand, and a new case was forgotten in it
    static let all: [DirectionOld] = [.north, .south, .east, .west]
}

// *** in version 4.2: ***
enum Direction: CaseIterable {
    case north, south, east, west
}

print(Direction.allCases.count)        // 4
for direction in Direction.allCases {
    print(direction)
}

let random = Direction.allCases.randomElement()

// the compiler builds allCases only for an enum without associated values;
// cases hidden behind @available are left out of it