FindObjectOfType returns destroyed object (leading to MissingReferenceException)

Hello all,

I have a problem when reloading a scene, after clicking the restart button and I invested maaanny hours now to find the reason without having success. So I really hope you can help me! :-)

My setup:

• GameManager

--- Singleton (destroying new intances)

--- set to DontDestroyOnLoad

--- gets himself a reference to a levelUIManager within the Update() method. This reference points to a actually destroyed instance after reloading the scene (see debug output below).

 private LevelUIManager levelUIManager;
 private void Update()
 {
     if (!gotOnce)
     {
         levelUIManager = FindObjectOfType<LevelUIManager>();
         Debug.Log("-------Game Manager Update-------- REF: " + levelUIManager.uuid);
         gotOnce = true;
     }
 }


    public void GameOver()
     {
         Debug.Log("---------GameOver--------LevelUIManager- UUID: " + levelUIManager.uuid);
         if (gameHasEnded == false)
         {
             gameHasEnded = true;
             levelUIManager.SetGameOver();
             levelUIManager.ShowGameOverUI();
             Debug.Log("Game Over");
         }
     }

• LevelUIManager

--- for debug purposes: generates a UUID within Awake() in order to know which intance I have

--- onDestroy(): shows the UUID of the destroyed instance .

 private void Awake()
 {
     uuid = Guid.NewGuid();
     Debug.Log("--------LevelUIManager - Awake-------UUID: " + uuid);
 }

 private void OnDestroy()
 {
     Debug.Log("Level UI Manager DESTROYED - UUID: " + uuid);
 }

If the restart button is hit, the Restart() of the GameManager is called:

 public void Restart()
 {
     GameManager.Instance.gotOnce = false;
     SceneManager.LoadScene(SceneManager.GetActiveScene().name);
 }

• PlayerCollision

--- within the OnCollisionEnter() I call the GameOver() method of my singleton instance of my GameManager

 GameManager.Instance.GameOver();

.

Output in the console shows that the wrong instance is returned within the seconds Game Manager Update and then used within the GameOver() which causes the problem I actually come from, a MissingReferenceException, which is logical if it uses a destroyed object...:

----------LevelUIManager - Awake---------UUID: a026f582-964d-4657-93dc-c222b24cfa7b ---------Game Manager Update-------- REF: a026f582-964d-4657-93dc-c222b24cfa7b ---------Game Manager Update-------- REF: a026f582-964d-4657-93dc-c222b24cfa7b
Level UI Manager DESTROYED - UUID: a026f582-964d-4657-93dc-c222b24cfa7b ---------LevelUIManager - Awake---------UUID: 3fa4f491-9038-40c5-9892-934ed9eea53b ---------GameOver--------LevelUIManager- UUID: 4fd23d3c-b0da-4d93-b29c-461678f36841

.

The only thing which caught my attention is the order in which the debug statments occur. Based on my understanding of the "order of execution for event functions" of MonoBehaviour classes I would have expected the following order:

• LevelUIManager Awake

• GameManager Update

• LevelUIManager Destroy (first action of the loading a new scene process)

• LevelUIManager Awake (as part of the instantiation, I expected this bevor the following update)

• GameManager Update

.

Is this understanding correct, and only the debug log statements have a wrong order, or can it be that the Update() of the GameManager really is executed before the new LevelUIManager is created (maybe because I dont destroy it?!?)

.

By the way: Formatting the text here to be readable is almost as challenging as game development... :-(