Question Index was outside the bounds of the array/System.Collections.Generic.List'1[T] - [SOLVED]

Hi devs, although I know the index exceeded the array limit, I don't see anything wrong with my code, but if any of you find something that makes sense for this error, please point me where I'm going wrong. Just an observation, I'm not referencing any array in the ispector, but I've tried referencing by dragging the gameobjects to the empty field of the array and it still didn't solve this error, so I know it's some incorrect logic in my code.

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine.SceneManagement;
4. using UnityEngine.UI;
5. using System;
6. using UnityEngine;
7.  
8. public class CarCheckpointManager : MonoBehaviour
9. {
10.     public int carNumber;
11.     public int checkpointCrossed = 0;
12.     public RaceManager raceManager;
13.     public int carPosition;
14.     public float timeAtLastPassedCheckpoint = 0;
15.     public Text PositionTxt;
16.     public static CarCheckpointManager instance;
17.     public event Action<CarCheckpointManager> OnPassCheckpoint;
18.  
19.     void Start()
20.     {
21.         instance = this;
22.     }
23.  
24.     private void OnTriggerEnter2D(Collider2D collision)
25.     {
26.         if(collision.gameObject.CompareTag("Checkpoint"))
27.         {
28.             checkpointCrossed += 1;
29.             raceManager.CarCollectedCheckpoints(carNumber, checkpointCrossed);
30.             timeAtLastPassedCheckpoint = Time.time;
31.             OnPassCheckpoint?.Invoke(this);
32.         }
33.     }
34.  
35.     public int GetNumberOfCheckpointsPassed()
36.     {
37.         return checkpointCrossed;
38.     }
39.  
40.     public float GetTimeAtLastPassedCheckpoint()
41.     {
42.         return timeAtLastPassedCheckpoint;
43.     }
44.  
45.     public void SetCarPosition(int position)
46.     {
47.         carPosition = position;
48.     }
49.  
50.     public void UpdateScore()
51.     {
52.         PlayerPrefs.SetInt("carPosition", carPosition);
53.     }
54. }

CODE 2°:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using System.Linq;
5.  
6. public class PositionHandler : MonoBehaviour
7. {
8.     LeaderBoardUIHandler leaderBoardUIHandler;
9.  
10.     [HideInInspector]
11.     public List<CarCheckpointManager> carCheckpointManagers = new List<CarCheckpointManager>();
12.  
13.     private void Awake()
14.     {
15.         CarCheckpointManager[] carCheckpointManagerArray = FindObjectsOfType<CarCheckpointManager>();
16.  
17.         carCheckpointManagers = carCheckpointManagerArray.ToList<CarCheckpointManager>();
18.  
19.         foreach (CarCheckpointManager carCheckpoint in carCheckpointManagers)
20.             carCheckpoint.OnPassCheckpoint += OnPassCheckpoint;
21.  
22.         leaderBoardUIHandler = FindObjectOfType<LeaderBoardUIHandler>();
23.     }
24.  
25.     private void Start()
26.     {
27.         leaderBoardUIHandler.UpdateList(carCheckpointManagers);
28.     }
29.  
30.     private void OnPassCheckpoint(CarCheckpointManager carCheckpoint)
31.     {
32.         carCheckpointManagers = carCheckpointManagers.OrderByDescending(s => s.GetNumberOfCheckpointsPassed()).ThenBy(s => s.GetTimeAtLastPassedCheckpoint()).ToList();
33.  
34.         int carPosition = carCheckpointManagers.IndexOf(carCheckpoint) + 1;
35.  
36.         carCheckpoint.SetCarPosition(carPosition);
37.  
38.         leaderBoardUIHandler.UpdateList(carCheckpointManagers);
39.     }
40. }
41.  

CODE 3°:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using TMPro;
5. using UnityEngine.UI;
6.  
7. public class LeaderBoardUIHandler : MonoBehaviour
8. {
9.     public GameObject leaderBoardItemPrefab;
10.  
11.     SetLeaderBoardItemInfo[] setLeaderBoardItemInfo;
12.  
13.     private void Awake()
14.     {
15.         VerticalLayoutGroup leaderBoardLayoutGroup = GetComponentInChildren<VerticalLayoutGroup>();
16.  
17.         CarCheckpointManager[] carCheckpointManager = FindObjectsOfType<CarCheckpointManager>();
18.  
19.         setLeaderBoardItemInfo = new SetLeaderBoardItemInfo[carCheckpointManager.Length];
20.  
21.         for (int i = 0; i < carCheckpointManager.Length; i++)
22.         {
23.             GameObject leaderBoardInfoGameObject = Instantiate(leaderBoardItemPrefab, leaderBoardLayoutGroup.transform);
24.  
25.             setLeaderBoardItemInfo[i] = leaderBoardInfoGameObject.GetComponent<SetLeaderBoardItemInfo>();
26.  
27.             setLeaderBoardItemInfo[i].SetPositionText($"{i + 1}.");
28.         }
29.     }
30.  
31.     public void UpdateList(List<CarCheckpointManager> carCheckpointManager)
32.     {
33.         for (int i = 0; i < carCheckpointManager.Count; i++)
34.         {
35.             setLeaderBoardItemInfo[i].SetDriverNameText(carCheckpointManager[i].gameObject.name);
36.         }
37.     }
38. }
39.  

 

I can't conclusively tell from your scripts but

setLeaderBoardItemInfo

is likely not the same length as

carCheckpointManager

.

I'd recommend attaching a debugger, breaking on on the IndexOutOfRangeException and checking the lengths. Being able to inspect the variables and check the stack gives you a different perspective and often makes issues much more obvious.

Note that there's two

carCheckpointManager

, an array you allocate in

LeaderBoardUIHandler

but also a list allocated in

PositionHandler

. The first is guaranteed to match in length to

setLeaderBoardItemInfo

but the second could well be different because of objects being unloaded or inactive and the second one gets passed into and used in

UpdateList

.

 

Thanks for the help, I'm still trying to solve it, but since you commented on the length of the other script, I'll send it here:

Code (CSharp):

1. public class SetLeaderBoardItemInfo : MonoBehaviour
2. {
3.     public TextMeshProUGUI positionText;
4.     public TextMeshProUGUI driverNameText;
5.  
6.     public void SetPositionText(string newPosition)
7.     {
8.         positionText.text = newPosition;
9.     }
10.  
11.     public void SetDriverNameText(string newDriverName)
12.     {
13.         driverNameText.text = newDriverName;
14.     }
15. }

 

Here are some notes on IndexOutOfRangeException and ArgumentOutOfRangeException:

http://plbm.com/?p=236

Steps to success:
- find which collection it is and what code accesses it (critical first step!)
- find out why it has fewer items than you expect
- fix whatever logic is making the indexing value exceed the collection
- remember you might have more than one instance of this script in your scene/prefab
- remember the collection may be used in more than one location in the code

 

I had just read your post about this, but I'm still trying to solve it, without success so far.

 

You might be missing my point.

LeaderBoardUIHandler.UpdateList

assumes the

setLeaderBoardItemInfo

array and the

carCheckpointManager

list have the same size, which doesn't have to be the case. Have you tried logging both sizes at the beginning of

UpdateList

?

 

Try putting this before the for loop in UpdateList:

Code (CSharp):

1. Debug.Log($"setLeaderBoardItemInfo.Length = {setLeaderBoardItemInfo.Length}, carCheckpointManager.Count = {carCheckpointManager.Count}");

Then trigger the out of range exception and check in the log if the two numbers don't match.

The log statement you tried to add is after the exception occurs, always put your log statement before the exception occurs and be careful not to trigger a new exception in the log statement itself. The exception will stop execution and anything after it will not be logged.

 

An interesting observation I had, I added the size of 3 in setLeaderBoardItemInfo[3], this way the errors don't appear, however the script doesn't show the names as it should.

 

As you can see in the log line right before the exception,

setLeaderBoardItemInfo

has length 4 but

carCheckpointManager

has count 5. When the for loop reaches the last item of

carCheckpointManager

(at index 4), it tries to access the corresponding item on

setLeaderBoardItemInfo

, but since that is only 4 items long (up to index 3), it tries to access index 4 that is out of bounds (4 > 3).

As I pointed out before, the fundamental issue is that

FindObjectsOfType

is only a snapshot. If you call it a different points in your game, it can return a different result because objects got instantiated, deleted, activated or deactivated. You create the

setLeaderBoardItemInfo

array based on the result of

FindObjectsOfType

at one point but then

UpdateList

is called at a different point in your game where

FindObjectsOfType

returns more results.

What the right approach to fixing this issue is really depends on your situation, you could:
- Ignore additional elements (change the for loop condition to

i < carCheckpointManager.Count && i < setLeaderBoardItemInfo.Length

)
- Instantiate additional

leaderBoardItemPrefab

and extend the

setLeaderBoardItemInfo

array so it contains enough elements (maybe turn it into list?)
- Don't pass in

carCheckpointManager

into

UpdateList

, instead store the

carCheckpointManager

you create in

LeaderBoardUIHandler.Awake

in a field and iterate that, since it will always stay the same length as

carCheckpointManager

.

 

Thank you very much for your help, this information will be very useful for me to solve this problem, I'll come back here when I have good news.

 

I would like to thank you again for the help, I changed the for loop as you suggested, and that alone has prevented the problem, and the good part is that even without the Debug.Log, the error does not appear.