ArgumentOutOfRangeException: Argument is out of range

Question

I have the following List:

public Question init()
{
     questions = new List<GameManager.Question>();
     questions.Add(new GameManager.Question("Ya no hay técnicas que te puedan salvar.", "Sí que las hay, sólo que nunca las has aprendido."));
     questions.Add(new GameManager.Question("Espero que tengas un barco para una rápida huida.", "¿Por qué? ¿Acaso querías pedir uno prestado?"));
     questions.Add(new GameManager.Question("Ahora entiendo lo que significan basura y estupidez.", "Me alegra que asistieras a tu reunión familiar diaria."));

     return questions;
}

I initialize the following buttons on start:

for (int i = 0; i < questionList.Count; i++)
{
    GameObject child = Instantiate(questionButton, buttonLayout.transform);
    child.GetComponent<Text>().text = questionList[i].answer;
    child.GetComponent<Button>().onClick.AddListener(() => QuestionCheck(i));
}

And I have the following code:

public void QuestionCheck(int index)
{
    if (currentQuestion.answer == questionList[index].answer)
    {
        playerAsk = 1;
        playerScore += 1;
        scorePlayer.GetComponent<Text>().text = "Jugador: " + playerScore;
        roundStatus.text = "Has ganado la ronda!";
        roundStatus.color = Color.green;
        correct.Play();
    }
}

I think it crashes on the following line:

if (currentQuestion.answer == questionList[index].answer)

Also if I try the following line it also crashes:

questionList.RemoveAt(index);

I obtain the following error:

ArgumentOutOfRangeException: Argument is out of range. Parameter name: index

Why this is happening?

EDIT: I've seen that the index from QuestionCheck is always 15, why this is happening?

also, why not use a dictionary? key can be the question, value can be the answer, and since no two questions should be the same, i think that would be better — traveler3468, Oct 11 '18 at 22:35
Its the index variable from QuestionCheck, it's always 15 but I don't know why (list goes from 0 to 14). — Lechucico, Oct 11 '18 at 22:35

score 2 · Accepted Answer · answered Oct 11 '18 at 22:43

2

This is scoping issue. Once the event happens, i is already at questionList.Count which is out of the array range. And all of your QuestionCheck will be called with questionList.Count (15 in your case)

What you want to do is save i to a temporary value, and used that instead:

for (int i = 0; i < questionList.Count; i++)
{
    var currentIndex = i;
    GameObject child = Instantiate(questionButton, buttonLayout.transform);
    child.GetComponent<Text>().text = questionList[i].answer;
    child.GetComponent<Button>().onClick.AddListener(() => QuestionCheck(currentIndex ));
}

answered Oct 11 '18 at 22:43

Lowkey

836
5
12

This worked, thanks! But I don't undestand why they all point to `i` instead of value. Isn't int a primitive type? – Lechucico Oct 11 '18 at 22:53
@Lechucico See [this question](https://stackoverflow.com/q/750486/1663383). Its a JavaScript question, but the underlying effects and reasons are the same. – Draco18s no longer trusts SE Oct 11 '18 at 23:56

score 2 · Answer 2 · answered Oct 11 '18 at 22:57

The problem is that your onClick listener is not evaluated within the loop but afterwards when the button is clicked.

child.GetComponent<Button>().onClick.AddListener(() => QuestionCheck(i));

So while i equals 0,1,3...14 while the loop runs, when your button is eventually clicked the loop has long since finished and i equals 15.

An easy fix to the problem is to create another variable that will hold the current value of i.

for (int i = 0; i < questionList.Count; i++)
{
    int questionIndex = i;
    GameObject child = Instantiate(questionButton, buttonLayout.transform);
    child.GetComponent<Text>().text = questionList[questionIndex].answer;
    child.GetComponent<Button>().onClick.AddListener(() => QuestionCheck(questionIndex));
}

score 0 · Answer 3 · answered Oct 11 '18 at 22:37

0

Argument out of range means in your case your list has 3 items, and its trying to access number 4, or 5 or anything higher than the range or count of your list.

also remember your list starts at 0, so your items are, 0,1, and 2

instead of

for (int i = 0; i < questionList.Count; i++)
{
    GameObject child = Instantiate(questionButton, buttonLayout.transform);
    child.GetComponent<Text>().text = questionList[i].answer;
    child.GetComponent<Button>().onClick.AddListener(() => QuestionCheck(i));
}

try

foreach(GameManager.Question q in questions){
    GameObject child = Instantiate(questionButton, buttonLayout.transform);
        child.GetComponent<Text>().text = q.answer;
        child.GetComponent<Button>().onClick.AddListener(() => QuestionCheck(i));
}

answered Oct 11 '18 at 22:37

Technivorous

1,682
2
16
22

How about the `i`? – Maurizio Carcassona Oct 11 '18 at 22:49
i can clarify. this is a for each, so basically its saying for each Question we will call q in questions do this... so the q, is your `i` its basically saying do this to each one, one at a time and just once. so where it says `q.answer` is equivalent to `questionList[i].answer;` – Technivorous Oct 11 '18 at 23:57
in that it will give you each answer in the list exactly one time. – Technivorous Oct 11 '18 at 23:58
I meant in `child.GetComponent – Maurizio Carcassona Oct 12 '18 at 10:09
1

Use q.index or questions.indexof(q) this will give u ints int value to pass to that method – Technivorous Oct 12 '18 at 13:27

ArgumentOutOfRangeException: Argument is out of range

3 Answers3