Event not being invoked

Question

I followed a Unity Events tutorial and adapted it to my game link: https://youtu.be/38D8AbR8TVU I have 1 script called GameLogicScript, 1 script called UIScript and 1 script for the events called Events

When I invoke an event from the UIScript, the GameLogicScript detects it and does accordingly how it is supposed to do, however, when I try to do it the other way (GameLogicScript invokes and event and UIScript detects it is not working) This is my relevant code:

--------------- UIScript ---------------

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class UIScript : MonoBehaviour
 {
     public GameObject pauseMenuUI;
     public GameObject gameOverMenuUI;
     public GameObject mainMenuUI;
     public GameObject gameplayUI;
     //Play - pause button
     public Button pauseResumeButton;
     public Sprite pauseSprite;
     public Sprite playSprite;
     //Score
     public Text scoreText;
     private int score;
 
     void Start()
     {
         //Listen to events
         Events.gameOver.AddListener(GameOver);
         Events.increaseScore.AddListener(IncreaseScore);
         Events.playAgainUI.AddListener(PlayAgain);
     }
 
     // Update is called once per frame
     void Update()
     {
         if(Input.GetKeyDown(KeyCode.Escape)){
             ResumeOrPause();
         }
     }
   
     public void PlayAgain(){
         Debug.Log("Holiwis");
         pauseMenuUI.SetActive(false);
         gameOverMenuUI.SetActive(false);
         mainMenuUI.SetActive(false);
         gameplayUI.SetActive(true);
     }
 
     public void PlayAgainForButton(){
         Events.playAgainGameLogic.Invoke();
     }
 }

--------------- GameLogicScript ---------------

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.SceneManagement;
 
 public class GameLogicScript : MonoBehaviour
 {
     //Cameras
     public GameObject menuCamera;
     public GameObject gameplayCamera;
     //Bool
     public static bool isPlaying = false;
     public static bool playAgain = false;
     //Float
     private float InstantiateToppingY;
     //GameObject
     private GameObject NextTopping;
     public GameObject NewToppingPrefab;
     //Others
     public Sprite[] ToppingSprites;
     
     void Start(){
         
         InstantiateToppingY = -2;
         //Listen to events
         Events.instantiateTopping.AddListener(InstantiateTopping);
         Events.resume.AddListener(Resume);
         Events.pause.AddListener(Pause);
         Events.mainMenu.AddListener(LoadMenu);
         Events.startGame.AddListener(StartGame);
         Events.playAgainGameLogic.AddListener(PlayAgain);
         
         if(playAgain){
             Debug.Log("Invoked event");
             Events.playAgainUI.Invoke();
             StartGame();
             
         }
         else
             Pause();
     }
 
     public void PlayAgain(){
         playAgain = true;
         SceneManager.LoadScene("Main");
     }
 }

--------------- Events ---------------

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.Events;
 
 public static class Events
 {
     public static UnityEvent gameOver = new UnityEvent();
     public static UnityEvent instantiateTopping = new UnityEvent();
     public static UnityEvent increaseScore = new UnityEvent();
     public static UnityEvent resume = new UnityEvent();
     public static UnityEvent pause = new UnityEvent();
     public static UnityEvent mainMenu = new UnityEvent();
     public static UnityEvent startGame = new UnityEvent();
     public static UnityEvent playAgainGameLogic = new UnityEvent();
     public static UnityEvent playAgainUI = new UnityEvent();
 
 }

Answer 1

Hi, I had a similar problem, Please change like this and should work.

 using System.Collections;
  using System.Collections.Generic;
  using UnityEngine;
  using UnityEngine.Events;
  
  public static class Events
  {
      public static UnityEngine.Events.UnityEvent gameOver = new UnityEngine.Events.UnityEvent();
      public static UnityEngine.Events.UnityEvent instantiateTopping = new UnityEngine.Events.UnityEvent();
      public static UnityEngine.Events.UnityEvent increaseScore = new UnityEngine.Events.UnityEvent();
      public static UnityEngine.Events.UnityEvent resume = new UnityEngine.Events.UnityEvent();
      public static UnityEngine.Events.UnityEvent pause = new UnityEngine.Events.UnityEvent();
      public static UnityEngine.Events.UnityEvent mainMenu = new UnityEngine.Events.UnityEvent();
      public static UnityEngine.Events.UnityEvent startGame = new UnityEngine.Events.UnityEvent();
      public static UnityEngine.Events.UnityEvent playAgainGameLogic = new UnityEngine.Events.UnityEvent();
      public static UnityEngine.Events.UnityEvent playAgainUI = new UnityEngine.Events.UnityEvent();
  
  }

Please let me know. You might have to change to this same pattern throughout the app.

Rgds

Answer 2

Answer by luislodosm · Mar 20 at 04:17 PM

Invoking an UnityEvent in Start() could produce a null reference.

 public UnityEvent event;
 
 void Start()
 {
    event.Invoke(); // Problem
 }

Instead, wait one frame:

 void Start()
 {
    StartCouroutine(InvokeCoroutine()); 
 }
 
 IEnumerator InvokeCoroutine()
 {
    yield return null;
    event.Invoke();
 }

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