Swift 4 Beta 5 NSKeyed{Una,A}rchiver Codable Support

KeyedCodable.swift

import Foundation

// Stolen from https://github.com/ole/whats-new-in-swift-4/blob/master/Whats-new-in-Swift-4.playground/Pages/Encoding%20and%20decoding.xcplaygroundpage/Contents.swift#L14-L31
struct Card: Codable, Equatable {
    enum Suit: String, Codable {
        case clubs, spades, hearts, diamonds
    }

    enum Rank: Int, Codable {
        case two = 2, three, four, five, six, seven, eight, nine, ten, jack, queen, king, ace
    }

    var suit: Suit
    var rank: Rank

    static func ==(lhs: Card, rhs: Card) -> Bool {
        return lhs.suit == rhs.suit && lhs.rank == rhs.rank
    }
}

let hand = [
    Card(suit: .clubs, rank: .ace),
    Card(suit: .hearts, rank: .queen)
] // => [{clubs, ace}, {hearts, queen}]

let a = NSKeyedArchiver()
try a.encodeEncodable(hand, forKey: "root")
let data = a.encodedData // => 499 bytes

let u = NSKeyedUnarchiver(forReadingWith: data)
let handAgain = try u.decodeDecodable(Array<Card>.self, forKey: "root") ?? [] // => [{clubs, ace}, {hearts, queen}]

handAgain == hand // true