event-bus

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

Scenario	Recommended approach
Parent notifying its own child	Direct signal or method call
Child notifying its parent	Direct signal (bubble up)
Two nodes with the same parent	Direct signal via parent
Completely unrelated nodes in the tree	Event bus
UI reacting to gameplay state changes	Event bus
Audio manager reacting to game events	Event bus
Data manager / save system reacting	Event bus
Tight, performance-sensitive inner loop	Direct method call