"Event Bus" Pattern in C#?

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1

Godot Version

v4.3.stable.mono.official [77dcf97d8]

Question

Can anyone explain (or point me toward a tutorial that does) how to make the “Event Bus” pattern in C#? I’ve only found resources on how to do this in GDScript, and I haven’t been able to figure out the conversion.

2

You can do it the same way as it’s done in gdscript. You make an autoload and define your signals there. Then you emit them via the autoload:

public partial class EventBus : Node {
  [Signal] 
  public delegate void SomeSignalEventHandler(string someParam);
}

// connect
GetNode<EventBus>("/root/EventBus").SomeSignal += SignalHandler;

// emit
GetNode<EventBus>("/root/EventBus").EmitSignal(EventBus.SignalName.SomeSignal, "param");

Of course you can also use C# events instead. Since you don’t need any node functionality or access to the scene-tree, you can make it a static class with static events.

public static class EventBus {
  // You could also use EventHandler with EventArgs to conform to the C# guidelines
  public static event Action<string> SomeEvent;

  // You need an extra function since events can only be invoked from the defining class
  public static void InvokeSomeEvent(string param) => SomeEvent?.Invoke(param);
}

// connect
EventBus.SomeEvent += SomeEventHandler;

// invoke
EventBus.InvokeSomeEvent("param");

If you are using static event you can also just define them in the relevant classes instead of having a separate EventBus class.

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