class Packet : NSObject,NSCoding {

  var tmp1: Double = 0
  var tmp2: Double = 0

  struct PropertyKey {
    static let tmp1Key = "tmp1Key"
    static let tmp2Key = "tmp2Key"
  }


  init(tmp1: Double,tmp2: Double) {
    self.tmp1 = tmp1
    self.tmp2 = tmp2
    super.init()
  }

  deinit {
  }

  required convenience init(coder aDecoder: NSCoder) {
    debugPrint("initcoder")
    let tmp1 = aDecoder.decodeObject(forKey: PropertyKey.tmp1Key) as! Double // crash here
    let tmp2 = aDecoder.decodeObject(forKey: PropertyKey.tmp2Key) as! Double
    self.init(tmp1: tmp1,tmp2: tmp2)
  }

  public func encode(with aCoder: NSCoder) {
    debugPrint("encodeCoder")
    aCoder.encode(tmp1,forKey: PropertyKey.tmp1Key)
    aCoder.encode(tmp2,forKey: PropertyKey.tmp2Key)
  }
}

我得到的错误是
—-打印出来—-“initcoder”
致命错误：在展开Optional值时意外发现nil
2016-09-30 13：32：55.901189连接[323：33022]致命错误：在解包可选值时意外发现nil

但是当我构造对象时,所有的值都被设置了.
我没有问题收缩了Packet对象.

– – 附加信息 – – –
当通过乘法器连接发送到另一侧时,我使用以下代码对数据进行编码和解码.

func dataForPacket(packet: Packet) -> Data {
    let data = NSMutableData()
    let archiver = NSKeyedArchiver(forWritingWith: data)
    archiver.encode(packet,forKey: "Packet")
    archiver.finishEncoding()
    debugPrint("dataForPacket \(data) \(packet)")
    return data as Data
  }

  func packetForData(_ data: Data) -> Packet {
    debugPrint("packetForData")
    let unarchiver = NSKeyedUnarchiver(forReadingWith: data)

    let packet: Packet = unarchiver.decodeObject(forKey: "Packet") as! Packet 
     // crash here (as this will call the init of the Packet class)
    debugPrint("packetForData \(packet)")
    return packet
  }

我想知道什么可能导致错误.谢谢.