# SyncVars SyncVars are properties of classes that inherit from NetworkBehaviour, which are synchronized from the server to clients. When a game object is spawned, or a new player joins a game in progress, they are sent the latest state of all SyncVars on networked objects that are visible to them. Use the `SyncVar` custom attribute to specify which variables in your script you want to synchronize. The state of SyncVars is applied to game objects on clients before `OnStartClient()` is called, so the state of the object is always up-to-date inside `OnStartClient()`. SyncVars can use any [type supported by Mirror](../DataTypes.md). You can have up to 64 SyncVars on a single NetworkBehaviour script, including SyncLists (see next section, below). The server automatically sends SyncVar updates when the value of a SyncVar changes, so you do not need to track when they change or send information about the changes yourself. Changing a value in the inspector will not trigger an update. > The [SyncVar hook](SyncVarHook.md) attribute can be used to specify a method to be called when the SyncVar changes value on the client. ## SyncVar Example Let's say we have a networked object with a script called Enemy: ``` cs public class Enemy : NetworkBehaviour { [SyncVar] public int health = 100; void OnMouseUp() { NetworkIdentity ni = NetworkClient.connection.identity; PlayerController pc = ni.GetComponent(); pc.currentTarget = gameObject; } } ``` The `PlayerController` might look like this: ``` cs public class PlayerController : NetworkBehaviour { public GameObject currentTarget; void Update() { if (isLocalPlayer) if (currentTarget != null) if (currentTarget.tag == "Enemy") if (Input.GetKeyDown(KeyCode.X)) CmdShoot(currentTarget); } [Command] public void CmdShoot(GameObject enemy) { // Do your own shot validation here because this runs on the server enemy.GetComponent().health -= 5; } } ``` In this example, when a Player clicks on an Enemy, the networked enemy game object is assigned to `PlayerController.currentTarget`. When the player presses X, with a correct target selected, that target is passed through a Command, which runs on the server, to decrement the `health` SyncVar. All clients will be updated with that new value. You can then have a UI on the enemy to show the current value. ## Class inheritance SyncVars work with class inheritance. Consider this example: ```cs class Pet : NetworkBehaviour { [SyncVar] String name; } class Cat : Pet { [SyncVar] public Color32 color; } ``` You can attach the Cat component to your cat prefab, and it will synchronize both it's `name` and `color`. > **Warning** Both `Cat` and `Pet` should be in the same assembly. If they are in separate assemblies, make sure not to change `name` from inside `Cat` directly, add a method to `Pet` instead.