NSKeyedArchiver自定义对象数组

Question

注意：Xcode 8 Beta 6

我不确定我缺少什么，但由于某种原因，我在NSKeyedArchiver.archivedData行上收到以下错误。

'NSInvalidArgumentException', reason: '-[_SwiftValue encodeWithCoder:]: unrecognized selector sent to instance 0x60000024c690'
*** First throw call stack:

这是我的类符合NSCoding协议：

enum PhraseType {
    case create
    case item
}

class Phrase: NSObject, NSCoding {

    var englishPhrase :String!
    var translatedPhrase :String!
    var phraseType :PhraseType! = PhraseType.item

    required init?(coder decoder: NSCoder) {

        self.englishPhrase = decoder.decodeObject(forKey: "englishPhrase") as! String
        self.translatedPhrase = decoder.decodeObject(forKey: "translatedPhrase") as! String
        self.phraseType = decoder.decodeObject(forKey: "phraseType") as! PhraseType
    }

    func encode(with coder: NSCoder) {

        coder.encode(self.englishPhrase, forKey: "englishPhrase")
        coder.encode(self.translatedPhrase, forKey: "translatedPhrase")
        coder.encode(self.phraseType, forKey: "phraseType")
    }

    init(englishPhrase :String, translatedPhrase :String) {

        self.englishPhrase = englishPhrase
        self.translatedPhrase = translatedPhrase

        super.init()
    }

}

以下是存档的代码：

 let userDefaults = UserDefaults.standard
        var phrases = userDefaults.object(forKey: "phrases") as? [Phrase]

        if phrases == nil {
            phrases = [Phrase]()
        }

        phrases?.append(phrase)

        let phrasesData = NSKeyedArchiver.archivedData(withRootObject: phrases)

        userDefaults.set(phrasesData, forKey: "phrases")
        userDefaults.synchronize()

有什么想法吗？