Mirror Spawning prefab from Client with client authority enabled crash due to command parameters bec

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Mirror Spawning prefab from Client with client authority enabled crash due to command parameters become null

My code in player prefab has a component script that contains the following for spawning a bullet.
It’s using ‘Mirror’. The ‘NetworkTransform’ has ClientAuthority enabled.

void Update()
    {
        if (!isLocalPlayer)
        {
            return; // dont run if not the local player
        }

        // .... some code....

        UpdateAction();

        // ..... more code ....
    }
 
    void UpdateAction()
    {
        if (targetOther != null)
        {
            Shoot();
            targetOther = null;
        }
    }

    void Shoot()
    {
        print("Bullet in Shoot : " + bullet + "\n is null ? " + (bullet == null));
        CmdShoot(bullet, transform.position + new Vector3(0, 2, 0), targetOther.gameObject);
    }

    [Command]
    public void CmdShoot(GameObject bulletPrefab, Vector3 spawnPos, GameObject targetOther)
    {
        print("Bullet Prefab : " + bulletPrefab +"\n is null ? " + (bulletPrefab == null));
        GameObject go = Instantiate(bulletPrefab);
        print(go);
        go.transform.position = spawnPos;
        HomingAttack ha;
        if (go.TryGetComponent<HomingAttack>(out ha))
        {
            ha._target = targetOther;
        }
        NetworkServer.Spawn(go);
    }

The GameObject bullet is a variable defined as public GameObject bullet; in the script. I have assigned this variable a proper prefab which has a NetworkIdentity and a NetworkTransform. Also, the prefab is added to registered spawnable prefabs.

The problem is the code crashes when this part of code is run ( it runs when I right click on another player ) since it reports that the bullet variable is null.
I have checked this with the print statements on line 26 and 33.
When run by the host-server player: line 26 prints that it has a valid value but line 33 prints that it is null.
How should I fix this?
Thank you.

2

Solved it.
Why the error occurred was that the prefab I am passing is not initialized in the server (instead I had it initialized in the client !!! which is wrong for my purpose).

Solution:
Instead of passing the GameObject prefab instance from the client to server, I must pass the index of the prefab from the registered spawnable prefabs.
Then in the server (command function) I locate the prefab instance by using NetworkManager.singleton.spawnPrefabs[index_of_bullet_prefab]

So for example the code is now like this:

void Shoot()
    {
        CmdShoot(0, transform.position + new Vector3(0, 2, 0), targetOther.gameObject);
    }
    [Command]
    public void CmdShoot(int prefabIdx, Vector3 spawnPos, GameObject targetOther)
    {

        GameObject go = Instantiate(NetworkManager.singleton.spawnPrefabs[prefabIdx]);
        print(go);
        go.transform.position = spawnPos;
        HomingAttack ha;
        if (go.TryGetComponent<HomingAttack>(out ha))
        {
            ha._target = targetOther;
        }
        NetworkServer.Spawn(go);
    }

This issue was not there for targetOther variable, I think this is because that gameObject exists in the server. Currently all my targetOther values are players (clients). Maybe that is why I can use that without a problem on contrast.

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