Mirror/doc/articles/Classes/SyncVars.md
2019-09-11 15:07:08 -04:00

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# 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](../Concepts/DataTypes.md). You can have up to 32 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.
> 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.playerController;
PlayerController pc = ni.GetComponent<PlayerController>();
pc.currentTarget = gameObject;
}
}
```
The `PlayerController` might look like this:
``` cs
public class PlayerController : NetworkBehaviour
{
public GameObject currentTarget;
void Update()
{
if (currentTarget != null)
if (currentTarget.tag == "Enemy")
if (Input.GetKeyDown(KeyCode.X))
CmdShoot(currentTarget);
}
[Command]
public void CmdShoot(GameObject enemy)
{
enemy.GetComponent<Enemy>().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.