ArgumentOutOfRangeException: Index was out of range. In a List>

Question

i was trying to make a List of different kinds of gathering blocks. But i wanted to make it so that there was only 1 in the inspector and then seperate them by category in code. I wanted to do this so the inspector did not get cluttered with different lists.

However after setting it up, i kept getting a error saying ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection.

Parameter name: index System.Collections.Generic.List`1[T].set_Item (System.Int32 index, T value) (at <9aad1b3a47484d63ba2b3985692d80e9>:0) BlockPlacing.Start () (at Assets/m/Scripts/BlockPlacing.cs:16)

My code/inspector list looks like this:

Inspector List Image

Code:

    [SerializeField] private List<GameObject> blocks = new List<GameObject>(64);
    private List<List<GameObject>> _mineralsList = new List<List<GameObject>>(4);

    void Start()
    {
        for (int j = 0; j < 4; j++)
        {
            for (int i = 0; i < 4; i++)
            {
                _mineralsList[j].Insert(i, blocks[i]);
            }
        }
    }

A different way of adding to the _mineralList i saw and tried was _mineralsList[j][i] = blocks[i] But that also didn't work and gave the same error.

The parameter that you pass to your list contructors doesn't mean that you have already that number of elements in the list. So when you write __mineralsList[j]_ and j is zero you get that error. First you need to Add some elements in that list — Steve, Feb 14 '23 at 13:21
In the same way the Insert called at index 0 when there is no element in the list will cause next a NullReferenceException. You need to create the inner list before trying to use any of its methods. — Steve, Feb 14 '23 at 13:23
@Steve ```_mineralsList[j] = new List(4);``` So i added this in the outer forloop. So it looks like this: for (int j = 0; j < blocks.Capacity / 4 / 4; j++) { _mineralsList[j] = new List(4); for (int i = 0; i < blocks.Capacity / 4 / 4; i++) { _mineralsList[j].Insert(i, blocks[i]); } } But it still gives the same error. I think this is what you meant? — Bloemenpot, Feb 14 '23 at 13:25
And _blocks[i]_ when i == 0? It doesn't exist an element of type GameObject at index 0 of that blocks list. Is the same as the previous problem 64/4 are just hints to the undelying list constructor that you expect to add 64/4 elements. It is not a request to create 64/4 GameObjects and insert them in the list — Steve, Feb 14 '23 at 13:34
@Steve im 99.9% certain that blocks[i] is not empty. Since when i Debug.Log(blocks[i]) it gives the GameObject that i inserted in the unity inspector. — Bloemenpot, Feb 14 '23 at 13:37

score 0 · Accepted Answer · answered Feb 14 '23 at 14:12

0

try to use this code:

public void Start()
{
    for (int j = 0; j < 4; j++)
    {
        _mineralsList.Add(new List<GameObject>());
        for (int i = 0; i < 4; i++)
        {
            if (i < blocks.Count) {
                _mineralsList[j].Add(blocks[i]);
            }
        }
    }
}

answered Feb 14 '23 at 14:12

Luca La Malfa

121
7

Hey, this worked. When i saw you're answer i immediately noticed what i was missing. I tried making the inner list in a way i would instantiate any object. But it has to be added since it is a list haha. Thank you very much! :D – Bloemenpot Feb 14 '23 at 14:20
you're welcome @Bloemenpot, please vote my anwser if it is usefully ;-) – Luca La Malfa Feb 16 '23 at 16:19
1

Hey, i tried to but i need atleast 15 reputation to upvote the answer, sorry :( – Bloemenpot Feb 18 '23 at 00:34

ArgumentOutOfRangeException: Index was out of range. In a List>

1 Answers1