컴포넌트 간 결합도를 끊어내는 제네릭 타입 기반 EventBus 시스템

using System;
using System.Collections.Generic;

public interface IEvent { }

public static class EventBus<T> where T : struct, IEvent
{
    private static readonly HashSet<Action<T>> _listeners = new HashSet<Action<T>>();

    public static void Subscribe(Action<T> listener)
    {
        if (listener != null) _listeners.Add(listener);
    }

    public static void Unsubscribe(Action<T> listener)
    {
        if (listener != null) _listeners.Remove(listener);
    }

    public static void Raise(T evt)
    {
        foreach (var listener in _listeners)
        {
            listener.Invoke(evt);
        }
    }

    public static void Clear() => _listeners.Clear();
}

// 1. 이벤트 데이터 정의
public readonly struct PlayerDamagedEvent : IEvent
{
    public readonly int Amount;
    public readonly int CurrentHp;

    public PlayerDamagedEvent(int amount, int currentHp)
    {
        Amount = amount;
        CurrentHp = currentHp;
    }
}

// 2. 수신처 (UI 컴포넌트)
public class HealthBarUI : UnityEngine.MonoBehaviour
{
    private void OnEnable() => EventBus<PlayerDamagedEvent>.Subscribe(OnPlayerDamaged);
    private void OnDisable() => EventBus<PlayerDamagedEvent>.Unsubscribe(OnPlayerDamaged);

    private void OnPlayerDamaged(PlayerDamagedEvent e)
    {
        UpdateHpGauge(e.CurrentHp);
    }
}

// 3. 발송처 (플레이어 컴포넌트)
// EventBus<PlayerDamagedEvent>.Raise(new PlayerDamagedEvent(15, 85));