Event System

Lightweight publish/subscribe system for decoupled communication between game systems.

Source: Assets/Scripts/Events/

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Overview

Event channels allow systems to communicate without direct references. A sender raises an event, and any number of subscribers receive it.

flowchart LR
    A[Sender] --> B[Event Channel]
    B --> C[Subscriber 1]
    B --> D[Subscriber 2]
    B --> E[Subscriber N]

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Event Channel Classes

The project uses simple C# classes (not ScriptableObjects) for events.

Source: EventChannel.cs

EventChannel<T>

Generic event channel for typed events.

public class EventChannel<T>
{
    private event Action<T> Handlers;

    public void Raise(T value) => Handlers?.Invoke(value);
    public void Subscribe(Action<T> handler) => Handlers += handler;
    public void Unsubscribe(Action<T> handler) => Handlers -= handler;
    public void Clear() => Handlers = null;
}

EventChannel (Void)

For events with no payload.

public class EventChannel
{
    private event Action Handlers;

    public void Raise() => Handlers?.Invoke();
    public void Subscribe(Action handler) => Handlers += handler;
    public void Unsubscribe(Action handler) => Handlers -= handler;
    public void Clear() => Handlers = null;
}

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Event Registries

Events are organized into static registry classes by category.

Source: Assets/Scripts/Events/Registries/

GameplayEvents

public static class GameplayEvents
{
    // Arena
    public static readonly EventChannel<int> PlayerDamaged = new();
    public static readonly EventChannel<int> PlayerHealed = new();
    public static readonly EventChannel<EnemyController> EnemySpawned = new();
    public static readonly EventChannel<EnemyController> EnemyDespawned = new();
    public static readonly EventChannel ArenaDefeatSequenceRequested = new();
    public static readonly EventChannel ArenaVictorySequenceRequested = new();

    // Stats
    public static readonly EventChannel<int> GoldChanged = new();
    public static readonly EventChannel<int> ExperienceChanged = new();
    public static readonly EventChannel<int> LevelChanged = new();

    // State
    public static readonly EventChannel GamePaused = new();
    public static readonly EventChannel GameResumed = new();
    public static readonly EventChannel<GameState> GameStateChanged = new();
    public static readonly EventChannel<ArenaState> ArenaStateChanged = new();

    public static void Clear() { /* clears all events */ }
}

AudioEvents

public static class AudioEvents
{
    public static readonly EventChannel<string> MusicRequested = new();
    public static readonly EventChannel<string> SfxRequested = new();
    public static readonly EventChannel<string> UISfxRequested = new();
    public static readonly EventChannel<string> AmbienceRequested = new();

    public static void Clear() { /* clears all events */ }
}

SystemEvents

public static class SystemEvents
{
    public static readonly EventChannel SettingsSaveRequested = new();
    public static readonly EventChannel SettingsLoadRequested = new();
    public static readonly EventChannel PlayerSaveRequested = new();
    public static readonly EventChannel PlayerLoadRequested = new();
    public static readonly EventChannel<Locale> LocaleChangeRequested = new();

    public static void Clear() { /* clears all events */ }
}

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Usage Examples

Subscribing to Events

public class GoldDisplay : MonoBehaviour
{
    private void OnEnable()
    {
        GameplayEvents.GoldChanged.Subscribe(UpdateDisplay);
    }

    private void OnDisable()
    {
        GameplayEvents.GoldChanged.Unsubscribe(UpdateDisplay);
    }

    private void UpdateDisplay(int newGold)
    {
        goldLabel.text = newGold.ToString();
    }
}

Raising Events

// When enemy dies
GameplayEvents.EnemyDespawned.Raise(controller);

// When gold changes
GameplayEvents.GoldChanged.Raise(newGoldAmount);

Requesting Audio

AudioEvents.SfxRequested.Raise("sword_hit");
AudioEvents.MusicRequested.Raise("combat_theme");

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Best Practices

Rule	Reason
Always unsubscribe in OnDisable	Prevents memory leaks and null reference errors
Keep handlers lightweight	Long handlers block other subscribers
Match subscribe/unsubscribe methods	Using different method references causes leaks

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Correct Pattern: Method Reference

// Correct - same method reference for subscribe and unsubscribe
private void OnEnable() => GameplayEvents.GoldChanged.Subscribe(HandleGoldChanged);
private void OnDisable() => GameplayEvents.GoldChanged.Unsubscribe(HandleGoldChanged);
private void HandleGoldChanged(int gold) { /* ... */ }

Incorrect Pattern (Memory Leak)

// Lambda creates new delegate each time - cannot unsubscribe
private void OnEnable() => GameplayEvents.GoldChanged.Subscribe(g => UpdateUI(g));
// This will NOT work - different delegate instance