JsonSerializationException: Unable to deserialize instance of 'BgDataMessage' for iOS on device..

When exporting my Unity project for iOS, the following exception is thrown during runtime:

JsonSerializationException: Unable to deserialize instance of ‘BgDataMessage’ because there is no parameterless constructor is defined on type.

It’s working fine while playing on Unity Editor. Unity version : 2020.2.2f1 Colyseus SDK version : 0.14.19

Following is the BgDataMessage.cs. class I’m using.

using System.Collections.Generic;

public class BgDataMessage
{
    public int max_win_streak, total_games_played, total_games_win;
    public float turn_timeout_seconds;
    public ulong bet_amount, max_bet_amount;
    public bool can_reconnect;
    public string _id, user_id, last_game_room_id, last_game_session_id;
    public Dictionary<string, List<long>> bet_ranges;
}

Here is how I’m registering for OnMessage: _roomLobby.OnMessage<BgDataMessage>(BgGameManager.MessageBgData, (bgData) => OnMessageBgData?.Invoke(bgData));

Xcode Stacktrace on Exception:

JsonSerializationException: Unable to deserialize instance of 'BgDataMessage' because there is no parameterless constructor is defined on type.
  at GameDevWare.Serialization.Metadata.TypeDescription.CreateInstance () [0x00000] in <00000000000000000000000000000000>:0 
  at GameDevWare.Serialization.Serializers.ObjectSerializer.PopulateInstance (GameDevWare.Serialization.IndexedDictionary`2[KeyT,ValueT] container, System.Object instance) [0x00000] in <00000000000000000000000000000000>:0 
  at GameDevWare.Serialization.Serializers.ObjectSerializer.Deserialize (GameDevWare.Serialization.IJsonReader reader) [0x00000] in <00000000000000000000000000000000>:0 
  at GameDevWare.Serialization.JsonReaderExtentions.ReadValue (GameDevWare.Serialization.IJsonReader reader, System.Type valueType, System.Boolean nextToken) [0x00000] in <00000000000000000000000000000000>:0 
  at System.Linq.Enumerable+<OfTypeIterator>d__97`1[TResult].System.Collections.IEnumerable.GetEnumerator () [0x00000] in <00000000000000000000000000000000>:0 
  at System.Runtime.CompilerServices.AsyncTaskCache.CreateCacheableTask[TResult] (TResult result) [0x00000] in <00000000000000000000000000000000>:0 
  at Colyseus.ColyseusRoom`1[T].ParseMessage (System.Byte[] bytes) [0x00000] in <00000000000000000000000000000000>:0 
  at NativeWebSocket.WebSocketMessageEventHandler.Invoke (System.Byte[] data) [0x00000] in <00000000000000000000000000000000>:0 
  at NativeWebSocket.WebSocket.DispatchMessageQueue () [0x00000] in <00000000000000000000000000000000>:0 
  at Colyseus.ColyseusClient+ColyseusAddRoomEventHandler.EndInvoke (System.IAsyncResult result) [0x00000] in <00000000000000000000000000000000>:0 
  at System.Threading.ContextCallback.Invoke (System.Object state) [0x00000] in <00000000000000000000000000000000>:0 
  at System.Threading.ExecutionContext.RunInternal (System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, System.Object state, System.Boolean preserveSyncCtx) [0x00000] in <00000000000000000000000000000000>:0 
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore+MoveNextRunner.Run () [0x00000] in <00000000000000000000000000000000>:0 
  at System.Action.Invoke () [0x00000] in <00000000000000000000000000000000>:0 
  at System.Threading.SendOrPostCallback.Invoke (System.Object state) [0x00000] in <00000000000000000000000000000000>:0 
  at UnityEngine.UnitySynchronizationContext.Exec () [0x00000] in <00000000000000000000000000000000>:0 
  at UnityEngine.UnitySynchronizationContext.Exec () [0x00000] in <00000000000000000000000000000000>:0 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x00000] in <00000000000000000000000000000000>:0 
  at System.Threading.SendOrPostCallback.Invoke (System.Object state) [0x00000] in <00000000000000000000000000000000>:0 
  at UnityEngine.UnitySynchronizationContext.Exec () [0x00000] in <00000000000000000000000000000000>:0 
  at UnityEngine.UnitySynchronizationContext.Exec () [0x00000] in <00000000000000000000000000000000>:0 
UnityEngine.UnitySynchronizationContext:Exec()
UnityEngine.UnitySynchronizationContext:Exec()

Kindly help me to resolve the issue ASAP as my game is ready and I’m not able to play it on device. Totally stuck! 😦

[VkDevPh]

Hi Edel, Do we have any update on it?

NullReferenceException at line no. 213 in Class MetadataReflection.cs.

I’m still stuck here and not able to play the game on an iOS device. waiting for a reply from your end.

Thanks

[deniszykov]

Hi @VkDevPh! This is case of Unity code stripping. You need to setup link.xml and make sure ILLinker would not delete constructor. As alternative solution you could reference anywhere in you code this constructor and it will retain.

if (typeof(string).Name == "") // any non true expression which is NOT compile time evaluable
{
    new BgDataMessage(...);
}

and this is bug in Unity’s runtime which should be reported:

NullReferenceException: Object reference not set to an instance of an object.
  at System.Linq.Expressions.Interpreter.LightLambda.MakeRunDelegateCtor (System.Type delegateType)