Unity3d Event Manager

EventManager.cs

 using System;
 using System.Collections.Generic;
 using System.Runtime.InteropServices;
 using UnityEngine;
 
 public class EventManager : MonoBehaviour
 {
 
     private Dictionary<string, Action<EventParam>> eventDictionary;
 
     private static EventManager eventManager;
 
     public static EventManager instance
     {
         get
         {
             if (!eventManager)
             {
                 eventManager = FindObjectOfType(typeof(EventManager)) as EventManager;
 
                 if (!eventManager)
                 {
                     Debug.LogError("There needs to be one active EventManger script on a GameObject in your scene.");
                 }
                 else
                 {
                     eventManager.Init();
                 }
             }
             return eventManager;
         }
     }
 
     void Init()
     {
         if (eventDictionary == null)
         {
             eventDictionary = new Dictionary<string, Action<EventParam>>();
         }
     }
 
     public static void StartListening(string eventName, Action<EventParam> listener)
     {
         Action<EventParam> thisEvent;
         if (instance.eventDictionary.TryGetValue(eventName, out thisEvent))
         {
             //Add more event to the existing one
             thisEvent += listener;
 
             //Update the Dictionary
             instance.eventDictionary[eventName] = thisEvent;
         }
         else
         {
             //Add event to the Dictionary for the first time
             thisEvent += listener;
             instance.eventDictionary.Add(eventName, thisEvent);
         }
     }
 
     public static void StopListening(string eventName, Action<EventParam> listener)
     {
         if (eventManager == null) return;
         Action<EventParam> thisEvent;
         if (instance.eventDictionary.TryGetValue(eventName, out thisEvent))
         {
             //Remove event from the existing one
             thisEvent -= listener;
 
             //Update the Dictionary
             instance.eventDictionary[eventName] = thisEvent;
         }
     }
 
     public static void TriggerEvent(string eventName, [Optional]  EventParam eventParam)
     {
         instance.eventDictionary[eventName](eventParam);
     }
 }
 
 public struct EventParam
 {
     public dynamic param;
 }

To trigger event:

EventParam eventParam = new EventParam();
eventParam.param = "test";
EventManager.TriggerEvent(Events.SHOW_TRUE_MODAL, eventParam);

to listen event:

 void OnEnable ()
    {
        EventManager.StartListening (Events.SHOW_TRUE_MODAL, ShowTrueModalListener);
    }

    void OnDisable ()
    {
        EventManager.StopListening (Events.SHOW_TRUE_MODAL, ShowTrueModalListener);
    }