Index was out of range. Must be non-negative and less than the size of the collection.

Unity Engine
1

Good day everyone. I’m still fairly new to unity, and as my first game I have been working on creating a visual memory card game.

I wanted to implement a restart button in my game that would reset the score count, however whenever I try to click on something in the scene that is NOT a card, I’m faced with an error, and I’m not sure what exactly is wrong with my code.

This is the part of my code in which I’m getting the error at:

    public Sprite board;

    public GameObject token;

    List<int> frontIndexes = new List<int>() { 0, 1, 2, 3, 0, 1, 2, 3 };

    public static System.Random random = new System.Random();
    public int shuffleNumber;

    SpriteRenderer spriteRenderer;

    void OnMouseDown()
    {
        int originalLength = frontIndexes.Count;
        float yPosition = 2.3f;
        float xPosition = -2.2f;

        if (spriteRenderer.sprite == board)
        {

            //creating this for loop in order to generate more clones
            for (int i = 0; i < 7; i++)
            {
                shuffleNumber = random.Next(0, frontIndexes.Count);
                Debug.Log(shuffleNumber);
                var temp = Instantiate(token, new Vector3(xPosition, yPosition, 0f),
                            Quaternion.identity);

                temp.GetComponent<FlippingCard>().frontIndex = frontIndexes[shuffleNumber];
                frontIndexes.Remove(frontIndexes[shuffleNumber]);

                xPosition = xPosition + 4;
                if (i == (originalLength/2 - 2))
                {
                    yPosition = -2.3f;
                    xPosition = -6.2f;
                }

            }
            token.GetComponent<FlippingCard>().frontIndex = frontIndexes[0];
        }
    }

The error I get is on line 36, where it says: temp.GetComponent<FlippingCard>().frontIndex = frontIndexes[shuffleNumber];

Error:

ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection
Parameter name: index
System.ThrowHelper.ThrowArgumentOutOfRangeException (System.ExceptionArgument argument, System.ExceptionResource resource) (at <9577ac7a62ef43179789031239ba8798>:0)
System.ThrowHelper.ThrowArgumentOutOfRangeException () (at <9577ac7a62ef43179789031239ba8798>:0)
System.Collections.Generic.List`1[T].get_Item (System.Int32 index) (at <9577ac7a62ef43179789031239ba8798>:0)
MakeVisible.OnMouseDown () (at Assets/Scripts/MakeVisible.cs:36)

I’ve been trying since yesterday to come up with a solution however I was unable to fix it. I’d really appreciate the help!

2

When you remove the number you’ve just used you do this:

frontIndexes.Remove(frontIndexes[shuffleNumber]);

That won’t remove the index you want, it’ll remove the value contained at that index (in your code it might remove 0,1,2 or 3 rather than the index which could be between 0 and 7). You would need to do this instead:

frontIndexes.Remove(shuffleNumber);
1 Like
3

Since OP posted this twice, let’s move all further replies to the thread with more replies already:

1 Like
4

I tried this, and it gave me the same error. :frowning: I just want to be able to click the reset button however whenever I try to click something that is not a card, I’m getting this index out of range error.

5

After the first click, the list will be empty and no index is valid on an empty list.

6

Looks like you’re trying to access the item which is not there in a list.