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[SyncVar]

[SyncVar] attribute is used to automatically synchronize variables from the server to clients. When the value changes on the server, it is automatically propagated to all clients.

Key Features​

  • One-way synchronization from server to client.
  • Changes made on the client are not synchronized back to the server.
  • Cannot be used with null values.
  • Supports basic types (e.g., int, long, float, string, Vector3) and GameObject types that include a NetworkIdentity.

Basic Use​

Syncing simple variables​

public class Player : NetworkBehaviour
{
    [SyncVar]
    public int health = 100;

    [SyncVar]
    public string playerName = "Player";

    [SyncVar]
    public Vector3 spawnPoint;
}

Using Hook Functions​

public class Player : NetworkBehaviour
{
    [SyncVar(hook = nameof(OnHealthChanged))]
    private int health = 100;

    // The hook function takes the previous value and the new value as parameters.
    private void OnHealthChanged(int oldValue, int newValue)
    {
        // Logic to execute when health changes
        UpdateHealthUI(newValue);
        PlayDamageEffect(oldValue - newValue);
    }
}

Synchronizing GameObject with NetworkIdentity​

public class PlayerEquipment : NetworkBehaviour
{
    [SyncVar]
    public GameObject currentWeapon;  // Only GameObjects with NetworkIdentity can be synced

    [Server]
    public void EquipWeapon(GameObject weapon)
    {
        if (!weapon.GetComponent<NetworkIdentity>())
            return;
            
        currentWeapon = weapon;
    }
}

Using Hook with GameObject​

public class PlayerTeam : NetworkBehaviour
{
    [SyncVar(hook = nameof(OnTeamChanged))]
    public GameObject currentTeam;  // GameObject with NetworkIdentity

    private void OnTeamChanged(GameObject oldTeam, GameObject newTeam)
    {
        // Logic to execute when team changes
        UpdateTeamUI();
        UpdatePlayerColor();
    }
}
note
  1. SyncVar values should only be changed on the server.
  2. Changing the SyncVar value on the client will not sync the value with other clients.
  3. The Hook function is automatically called whenever the value of a SyncVar changes.
  4. When using a GameObject as a SyncVar, the NetworkIdentity component is required. :::