NSCoding a Swift Enum

EnumNSCoding.swift

//: Playground - noun: a place where people can play

import Cocoa

enum Enum {
    case SimpleCase
    case AssociatedValue(String)
    case AnotherAssociated(Int)
}
extension Enum {
    enum Base: String {
        case SimpleCase
        case AssociatedValue
        case AnotherAssociated
    }
    var base: Base {
        switch self {
        case .SimpleCase:        return .SimpleCase
        case .AssociatedValue:   return .AssociatedValue
        case .AnotherAssociated: return .AnotherAssociated
        }
    }
}

class Class: NSObject, NSCoding {
    var e: Enum
    
    // Memberwise initializer
    init(e: Enum) {
        self.e = e
    }
    
    // MARK: NSCoding
    required convenience init?(coder decoder: NSCoder) {
        guard
            let rawCase = decoder.decodeObjectForKey("case") as? String,
            let base = Enum.Base(rawValue: rawCase)
        else { return nil }
        
        let e: Enum
        switch base {
        case .SimpleCase:
            e = .SimpleCase
        case .AssociatedValue:
            guard
                let value = decoder.decodeObjectForKey("value") as? String
                else { return nil }
            e = .AssociatedValue(value)
        case .AnotherAssociated:
            let value = decoder.decodeIntegerForKey("value")
            e = .AnotherAssociated(value)
        }
        self.init(e: e)
    }
    
    func encodeWithCoder(coder: NSCoder) {
        coder.encodeObject(e.base.rawValue, forKey: "case")
        switch e {
        case .SimpleCase: break
        case .AssociatedValue(let value):   coder.encodeObject(value, forKey: "value")
        case .AnotherAssociated(let value): coder.encodeInt(Int32(value), forKey: "value")
        }
    }
}

let e = Class(e: .AnotherAssociated(154))
let arcvd = NSKeyedArchiver.archivedDataWithRootObject(e)
let unarc = NSKeyedUnarchiver.unarchiveObjectWithData(arcvd)
let c = unarc as? Class
c?.e