SimpleBus Event Bus for Unity

A lightweight generic event bus system for Unity, allowing decoupled communication between components using strongly-typed events.

This system supports:

• Registering listeners for events
• Raising events with or without arguments
• Automatic type safety using generics

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Installation

You can add DumbInjector to your Unity project in two ways:

Option 1: Git Submodule

git submodule add https://github.com/oultrox/SimpleBus.git Assets/SimpleBus

Option 2: Unity Package Manager

1. Open Window > Package Manager
2. Click the + button and choose Add package from git URL
3. Enter:

https://github.com/oultrox/SimpleBus.git

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Core Concepts

IEvent

All events should implement the IEvent interface.

public interface IEvent { }

EventBus

The generic static event bus class.

• T must implement IEvent.
• Supports Register, Deregister, and Raise methods.

EventBus<MapGeneratedEvent>.Raise(new MapGeneratedEvent());

IEventListener & EventListener

• IEventListener<T> defines event callbacks.
• EventListener<T> is a concrete class you can instantiate with actions.

public class EventListener<T> : IEventListener<T> where T : IEvent
{
    public Action<T> OnEvent { get; set; }
    public Action OnEventNoArgs { get; set; }

    // Constructors and add/remove helpers included
}

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Step 1: Define Your Event

Events must implement the IEvent interface.
It’s usually preferred to define them as structs since they are lightweight and reduce allocations:

// Events can be empty
public struct MapGeneratedEvent : IEvent{} 

// Or have parameters
public struct ShowMazePathEvent : IEvent
{
    public string mazePathName;
}

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Step 2: Register a Listener

Create a listener and register it with the EventBus:

private EventListener<MapGeneratedEvent> _mapGeneratedListener;

public MazeGenerator(IPathFinder pathFinder, IEntitySpawner spawner)
{
    _mapGeneratedListener = new EventListener<MapGeneratedEvent>(Generate);
    EventBus<MapGeneratedEvent>.Register(_mapGeneratedListener);
}

// Event callback
void Generate(MapGeneratedEvent e)
{
    Debug.Log("Map generated!");
}

You can also register listeners without arguments:

new EventListener<ShowMazePathEvent>(() => ShowPath()).Add(...);

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Step 3: Raise an Event

Any component can raise an event, and all registered listeners will be notified:

//Example
void GenerateMap()
{
    EventBus<MapGeneratedEvent>.Raise(new MapGeneratedEvent());
}

void ShowPath()
{
    EventBus<ShowMazePathEvent>.Raise(new ShowMazePathEvent());
}

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Step 4: Deregister a Listener

When a listener is no longer needed (e.g., on destroy):

EventBus<MapGeneratedEvent>.Deregister(_mapGeneratedListener);

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Full Example

public class MazeManager : MonoBehaviour
{
    private readonly MapGeneratedEvent _mapGenerated = new();
    private readonly ShowMazePathEvent _showMazePath = new();

    void Start()
    {
        InjectListeners();
    }

    void InjectListeners()
    {
        generateButton.onClick.AddListener(() => EventBus<MapGeneratedEvent>.Raise(_mapGenerated));
        showPathButton.onClick.AddListener(() => EventBus<ShowMazePathEvent>.Raise(_showMazePath));
    }
}

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Notes

• Listeners can subscribe multiple actions.
• Events are type-safe, avoiding the need for string-based events.
• Supports both argument and no-argument callbacks.
• EventBus<T>.Clear() can reset all listeners for a specific type (useful for editor testing).

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Suggested Usage

• Decouple systems: UI can listen to GameLogic events without direct references.
• Avoid tight coupling: Components don’t need to know who is listening.

Future improvements

• Debug configurations to let the users disable the logs.