Can't inherit from NetworkVariable

[matthieu-blin]

Description

Since NetworkBehaviour use IsSubclassOf(NetworkVariableBase) and IsSubclassOf use BaseType we're forced to inherit directly from NetworkVariableBase

Context :

During a Unet to Netcode translation, i wanted to avoid the throw when setting a NetworkVariable from client since Unet was fine with this even in incorrect case. Inheriting from NetworkVariable just to override Value property seems a quick way for this.

Expected :

Either forbid this sealing NetworkVariable (and that's fine) or allow it (changing IsSubClass for a IsAssignableFrom or kind of)

[NoelStephensUnity]

@matthieu-blin
Could you provide the exception thrown along with the version of NGO and Unity you are using?

[matthieu-blin]

Unity 2020.3.40f1 NGO 1.2.0
but btw : here a direct link

com.unity.netcode.gameobjects/com.unity.netcode.gameobjects/Runtime/NetworkVariable/NetworkVariable.cs

Line 60 in 4a1c2ff

throw new InvalidOperationException("Client is not allowed to write to this NetworkVariable");

[NoelStephensUnity]

@matthieu-blin
Thank you for that information as it does help me narrow this down.
Just to get a bit more context about the NetworkVariable instance in question:

• Should all clients and the server/host be able to write to it?
  • If not, then is it just the server and the client question that should be able to write to it?

With the above information I will better understand the context of this issue and be better able to determine the scope of change required. However, in the name of saving time... 😸

My first pass guess is that the ability to override the NetworkVariableBase.CanClientWrite method might resolve the issue you ran up against?

If that is the case, would something like the following provide the type of functionality you are looking for?

/// <summary>
/// Override this method to apply your own permissions
/// </summary>
/// <param name="clientId">The client id</param>
/// <returns>The client id</returns>
protected virtual bool OnCanClientWrite(ulong clientId)
{
    switch (WritePerm)
    {
        default:
        case NetworkVariableWritePermission.Server:
            return clientId == NetworkManager.ServerClientId;
        case NetworkVariableWritePermission.Owner:
            return clientId == m_NetworkBehaviour.NetworkObject.OwnerClientId;
    }
}

/// <summary>
/// Gets if a specific client has permission to write the var or not
/// </summary>
/// <param name="clientId">The client id</param>
/// <returns>The client id</returns>
public bool CanClientWrite(ulong clientId)
{
    return OnCanClientWrite(clientId);
}

Where the same modification would be applied to NetworkVariableBase.CanClientRead in order to provide full (read & write) control over permissions.

[matthieu-blin]

well it could (and that could be a cool feat btw) , but you're running around the real issue here
=> We can't inherit from networkVariable.

Eventually i assume i could inherit from NetworkVariableBase and copy paste all the code from NetworkVariable into a MyNetworkVariable but i'm not sure it's designed that way.

[NoelStephensUnity]

@matthieu-blin
Apologies for not better understanding the issue you are having.
You should be able to derive from NetworkVariable<T>.
To double check, I just tested the following:

    public class MyCustomNetworkVariable<T> : NetworkVariable<T>
    {
        public override T Value
        {
            get
            {
                Debug.Log($"[{typeof(T).Name}] Overridden Value getter invoked!");
                return base.Value;
            }
            set
            {
                Debug.Log($"[{typeof(T).Name}] Overridden Value setter invoked with value being set to: {value}!");
                base.Value = value;
            }
        }
        public override bool IsDirty()
        {
            Debug.Log($"[{typeof(T).Name}] Overridden IsDirty invoked!");
            return base.IsDirty();
        }
    }

It seems to work as expected:

Perhaps you can provide me with an example of what is not working for you?
That would help me further narrow down what use case scenario you are running into that does not allow you to derive from NetworkVariable<T>.

[matthieu-blin]

oh no don't apology, if you can't pinpoint the bug easily, either my explanations were not clear enough or i just make some dumb assumption (i just read the github code at that time, not retrieve it) or both !

So i performed some tests earlier this morning : can't reproduce the issue despite i double and tripled checked first time before submitting.

First i assumed it was an issue with assembly/domain (since the report, we forked ngo into our repository). But don't seems so.

Could also be in 1.1.0 or even 1.0.0 (just checked when you told me to, and can't remember if i upgraded after report neither i can't find the information due to multiple branching at that time )

Could also just be a timing issue : did i really check that object were spawn at that time ? Was i testing against the Unet time of variable registering ? Since i was in a middle of the migration , a lot of stuff were broken.

So anw, sorry for the time spend on this and thanks for your support. You can close this
For others issue, i will provide a pull request btw with a basic sample code for you to test.

[NoelStephensUnity]

No worries at all.
Thank you for checking this again on your side and confirming the issue does not occur in v1.2.0.
Regarding future issues, it always helps to have some kind of code reference that replicates the issue. That would definitely help get faster response times and is a big help to us on this end! 👍