Class EventBus

A global container that maps Event names and Component references to actions for registered listeners.

Inheritance
object
EventBus
Inherited Members
Namespace: Unity.VisualScripting
Assembly: Unity.VisualScripting.Core.dll
Syntax
public static class EventBus
Remarks

It is the EventMachine base class for ScriptMachine and StateMachine that triggers events. This overrides almost all Unity callbacks (such as Awake, OnEnable, Update, etc.) and triggers an event on the EventBus.

Examples

The following example shows how to use the EventBus to send a custom event from a script to a node in a graph. It also shows how to use the EventBus as a global event manager by executing a callback in a script, not just a node.

For more information on how to create custom event nodes refer to the User Manual.

In this example we've added some code to a GameObject. This code checks for when the user presses a sequence of keys to enable a cheat code, then triggers the CheatCodeActivated event. We register the CheatCodeActivated event in the Start method. The Update method triggers the event twice with 2 different targets: one for the CheatCodeActivated callback and the other to trigger the CheatCodeEnabled Node.

public class CheatCodeController : MonoBehaviour
{
    public const string CheatCodeActivated = "CheatCodeActivated";

    static readonly KeyCode[] famousCheatCode = {
        KeyCode.UpArrow,
        KeyCode.UpArrow,
        KeyCode.DownArrow,
        KeyCode.DownArrow,
        KeyCode.LeftArrow,
        KeyCode.RightArrow,
        KeyCode.LeftArrow,
        KeyCode.RightArrow,
        KeyCode.B,
        KeyCode.A
    };

    int index;
    EventHook cheatCodeHook;
    Action<EmptyEventArgs> godModeDelegate;

    // A GameObject with a ScriptMachine that holds a graph with a
    // CheatCodeEnabled Event Node.
    public GameObject player;

    void Start()
    {
        // Hold a reference to the EventHook and the Delegate for the
        // EventBus.Unregister call in the OnDestroy method.
        cheatCodeHook = new EventHook(CheatCodeActivated);
        godModeDelegate = _ => EnableGodMode();

        EventBus.Register(cheatCodeHook, godModeDelegate);
    }

    void Update()
    {
        if (Input.anyKeyDown)
        {
            if (Input.GetKeyDown(famousCheatCode[index]))
            {
                index++;
            }
            else
            {
                index = 0;
            }

            if (index >= famousCheatCode.Length)
            {
                // Triggers the EnableGodMode delegate
                EventBus.Trigger(CheatCodeActivated);

                // Triggers the CheatCodeEnabled Visual Scripting Node
                EventBus.Trigger(new EventHook(
                    CheatCodeActivated,
                    player.GetComponent<ScriptMachine>()));

                index = 0;
            }
        }
    }

    void OnDestroy()
    {
        EventBus.Unregister(cheatCodeHook, godModeDelegate);
    }

    void EnableGodMode()
    {
        Debug.Log("Cheat code has been entered. Enabling god mode.");
    }
}

The CheatCodeEnabled Node:

[UnitTitle("On Cheat Code Enabled")]
public sealed class CheatCodeEnabled : MachineEventUnit<EmptyEventArgs>
{
    protected override string hookName => CheatCodeController.CheatCodeActivated;
}

Methods

Register<TArgs>(EventHook, Action<TArgs>)

Declaration
public static void Register<TArgs>(EventHook hook, Action<TArgs> handler)
Parameters
Type Name Description
EventHook hook
Action<TArgs> handler
Type Parameters
Name Description
TArgs

Trigger(string, GameObject)

Declaration
public static void Trigger(string name, GameObject target)
Parameters
Type Name Description
string name
GameObject target

Trigger(EventHook)

Declaration
public static void Trigger(EventHook hook)
Parameters
Type Name Description
EventHook hook

Trigger<TArgs>(string, GameObject, TArgs)

Declaration
public static void Trigger<TArgs>(string name, GameObject target, TArgs args)
Parameters
Type Name Description
string name
GameObject target
TArgs args
Type Parameters
Name Description
TArgs

Trigger<TArgs>(EventHook, TArgs)

Declaration
public static void Trigger<TArgs>(EventHook hook, TArgs args)
Parameters
Type Name Description
EventHook hook
TArgs args
Type Parameters
Name Description
TArgs

Unregister(EventHook, Delegate)

Declaration
public static void Unregister(EventHook hook, Delegate handler)
Parameters
Type Name Description
EventHook hook
Delegate handler