NullReferenceException on OnEnable function

Hi this maybe a silly question but this is the first time I met this error when using OnEnable function. So the script is like this:
Quiz.cs

Code (CSharp):

1. private void OnEnable()
2.     {
3.         QuizManager.I.Reposition(rt);
4.         QuizManager.I.MakeQuiz(this);
5.     }

QuizManager.cs

Code (CSharp):

1. public void MakeQuiz(Quiz quiz)
2.     {
3.         TileType[] ttArr;
4.         ShuffleQuiz(out ttArr);
5.  
6.         quiz.displayID = (int)ttArr[0];
7.         quiz.displayImg.sprite = collection.GetSpriteFromTileID(ttArr[0]);
8.  
9.         quiz.qP[0].choiceID = (int)ttArr[1];
10.         quiz.qP[1].choiceImg.sprite = collection.GetSpriteFromTileID(ttArr[1]);
11.  
12.         quiz.qP[1].choiceID = (int)ttArr[2];
13.         quiz.qP[2].choiceImg.sprite = collection.GetSpriteFromTileID(ttArr[2]);
14.     }

it said I have null reference on

QuizManager.I.MakeQuiz(this);

so I wrote a line of code on Awake() function

q = GetComponent<Quiz>();

and passed it to MakeQuiz function but no luck.
Any help will be appreciated. Thanks

 

Use Log.Debug to make sure all the separate parts you are accessing are really present:

Code (CSharp):

1.  
2. private void OnEnable()
3. {
4.     Debug.Log("QM is " + QuizManager.name);
5.     Debug.Log("I is " + QuizManager.I.name);
6.     Debug.Log("RT is " + rt.name);
7.     QuizManager.I.Reposition(rt);
8.     Debug.Log("First Access Done");
9.     QuizManager.I.MakeQuiz(this);
10. }
11.  

I'm betting it's not 'this' that causes the problem, but "I" or "QuizManager"

 

My bad I made a simple mistake. The problem was in the variable

displayImg

I put [HideInInspector] that make the reference null. I think I need some coffee

 

Glad to hear that it is working now.

A small aside that you probably know already:

HideInInspector will not make the contents of a variable null. It merely makes it inaccessible via the Inspector. But since displayImg is a class variable, it is initialized upon class instancing. If you did not initialize that variable to a default value during declaration, it will be initialized to null.

You can verify this by trying the following:

Code (CSharp):

1. [HideInInspector]
2. List<string> L = new List<string>();// initialize this variable to a valid List

and then a access L - you'll find it will NOT be null.