Event Bus in Godot 4.3+

A global signal hub that lets unrelated nodes communicate without holding references to each other. All examples target Godot 4.3+ with no deprecated APIs.

Related skills: component-system for direct signal communication between components, csharp-signals for C#-specific signal patterns, dependency-injection for alternative decoupling approaches, ability-system for an EventBus usage example with ability events.

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1. What is an Event Bus

An EventBus is a singleton autoload that acts as a central registry for signals. Instead of nodes connecting directly to each other, every node connects to (or emits on) the shared EventBus. This removes the need for one node to hold a reference to another.

Without EventBus             With EventBus
──────────────               ──────────────────────────
NodeA ──signal──► NodeB      NodeA ──emit──► EventBus ──signal──► NodeB
                                                       ──signal──► NodeC
                                                       ──signal──► NodeD

Flow diagram

┌─────────┐   emit(player_died)   ┌───────────┐   player_died   ┌──────────┐
│  NodeA  │ ────────────────────► │ EventBus  │ ───────────────► │  NodeB   │
│(Player) │                       │(Autoload) │                  │   (UI)   │
└─────────┘                       └───────────┘ ───────────────► └──────────┘
                                                  player_died    ┌──────────┐
                                                                 │  NodeC   │
                                                                 │(AudioMgr)│
                                                                 └──────────┘

NodeA emits the signal. NodeB and NodeC each connected to EventBus independently. Neither knows the other exists.

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2. When to Use vs Direct Signals