Question How can I create a NetworkList/NetworkVariable<List> of lists?

I'm trying to create a game where players take turns drawing to their screens. I need a list of Vector2 points (for each paint stroke), and then I need a list of these strokes to show a full drawing.

Traditionally, I would create a List<List<Vector2>> but since I want this information stored on and shared from my server, I need a NetworkVariable or NetworkList to keep track of everyone's paint strokes.

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Attempt 1
My code initializing my NetworkList of lists:

Code (CSharp):

1. public NetworkList<List<Vector2>> playerStrokes = new NetworkList<List<Vector2>>(default, NetworkVariableBase.DefaultReadPerm, NetworkVariableWritePermission.Owner);

This code gives the following error:

error CS8377: The type 'List<Vector2>' must be a non-nullable value type, along with all fields at any level of nesting, in order to use it as parameter 'T' in the generic type or method 'NetworkList<T>'

This error doesn't make sense because Lists are non-nullable by default, and Vector2's are structs.

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Attempt 2
I've also tried creating an INetworkSerializable of Vector2[], but I'm getting the same error..

Code (CSharp):

1. [System.Serializable]
2. public struct NetworkListOfStrokes : INetworkSerializable
3. {
4.     public int playerIndex;
5.     public Vector2[] strokes;
6.  
7.     public NetworkListOfStrokes(int _playerindex, Vector2[] _strokes)
8.     {
9.         playerIndex = _playerindex;
10.         strokes= _strokes;
11.     }
12.  
13.     public void NetworkSerialize<T>(BufferSerializer<T> serializer) where T : IReaderWriter
14.     {
15.         serializer.SerializeValue(ref playerIndex);
16.         serializer.SerializeValue(ref strokes);
17.     }
18. }

Code (CSharp):

1. public NetworkList<NetworkListOfStrokes> playerStrokes2 = new NetworkList<NetworkListOfStrokes>(default, NetworkVariableBase.DefaultReadPerm, NetworkVariableWritePermission.Owner);

and the error is

error CS8377: The type 'NetworkListOfStrokes' must be a non-nullable value type, along with all fields at any level of nesting, in order to use it as parameter 'T' in the generic type or method 'NetworkList<T>'

It seems netcode really just doesn't want me to have nested lists. Has anybody been able to get a list of lists working in netcode? I'll update this post if I find the solution.

 

Hello!
I found something close to a solution in the documentation, see there if it helps you:

https://docs-multiplayer.unity3d.co...x.html#custom-networkvariable-implementations

Basically, you have to create your own type of NetworkVariable.

Hope this helps