         let dic = NSMutableDictionary()
         for (k, v) in self {
             // 第一步序列化key
-            if let k = _serialize(k) as? NSCopying {
+            if let k = _serialize(k) {
                 // 只支持转换为`NSString`
                 guard let k = NSString.deserialize(k) else {
                     continue

    public static func deserialize(o: AnyObject) -> UInt? {
        // 如果可以的话转换一下..
        if let number = NSNumber.deserialize(o) {
            return number.unsignedIntegerValue
        }
        return nil
    }

    /// 序列化
    ///
    public func serialize() -> AnyObject? {
        return NSNumber(unsignedLong: self)
    }
    ///
    /// 反序列化
