[CreateAssetMenu(menuName = "Scriptable Objects/ Game Event")]
public class GameEvent : ScriptableObject {

    private List<GameEventListener> listeners = new List<GameEventListener>();

    public void Raise()
    {
        for (int i = listeners.Count - 1; i >= 0; i--)
        {
            if(listeners[i] != null)
            {
                listeners[i].OnEventRaised();
            }
        }
    }

    public void RegisterListener(GameEventListener listener)
    {
        if (listeners.Contains(listener))
            return;
        listeners.Add(listener);
    }

    public void UnregisterListener(GameEventListener listener)
    {
        if (!listeners.Contains(listener))
            return;
        listeners.Remove(listener);
    }
}