swift – 如何使用NSKeyedUnarchiver的代理？

我正在使用NSKeyedUnarchiver来取消归档对象并希望使用委托(NSKeyedUnarchiverDelegate),但我的代理不会被调用.归档和取消归档工作正常,但代理(unarchiver& unarchiverDidFinish)未被调用.有人可以帮忙吗？

我有以下实现：

class BlobHandler: NSObject , NSKeyedUnarchiverDelegate{

           func load() -> MYOBJECTCLASS{          
              let data:NSData? = getBlob();      
              var mykeyedunarchiver:NSKeyedUnarchiver=NSKeyedUnarchiver(forReadingWithData: data!);
              mykeyedunarchiver.delegate = self;
              let temp=mykeyedunarchiver.decodeObjectForKey("rootobject")
// No delegates are called
                            if temp==nil {
                                blobsexists=false;
                            }else{
                                objectreturn = temp! as! MYOBJECTCLASS;
                                return objectreturn;
                            }
        }

    func save1(myobject:MYOBJECTCLASS){
            let data = NSMutableData()
            var keyedarchiver:NSKeyedArchiver=NSKeyedArchiver(forWritingWithMutableData: data);
            keyedarchiver.encodeObject(maptheme, forKey: "rootobject");

            let bytes = data.bytes;
            let len=data.length; 
            saveblob(bytes);
    }

从未调用以下代理,这些代理也在我的Blobhandler中实现：

func unarchiver(unarchiver: NSKeyedUnarchiver, cannotDecodeObjectOfClassName name: String, originalClasses classNames: [String]) -> AnyClass? {
    print("I am in unarchiver !");
    return nil;
}

func unarchiverDidFinish(_ unarchiver: NSKeyedUnarchiver){
    print("I am in unarchiverDidFinish ! ");
}