How can I write a Random.Range Scripts without repetition?

Hello! Thanks for watching my question.
I want to make boxes on the chessboard and the boxes are randomly created.
When player get a box, box disappears and with some seconds later, boxes are recreated.
So I tried this script, but when I play this script, boxes are successfully randomly created without repetition, but when boxes are fully created, Unity Engine stops and I can't do anything in Unity Engine.
And when I get a box before boxes are fully created, a box isn't recreated.
I'm sorry for my bad English. How can I fix this problem?

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class SpawnMgr : MonoBehaviour
6. {
7.     public Transform[] points;
8.     public GameObject boxPrefab;
9.  
10.     public float createTime = 2.0f;
11.     public int maxBox = 10;
12.  
13.     public bool isGameOver = false;
14.  
15.     List<int> list = new List<int>();
16.  
17.     void Start()
18.     {
19.         points = GameObject.Find("SpawnPoint").GetComponentsInChildren<Transform>();
20.  
21.         if(points.Length > 0)
22.         {
23.             StartCoroutine(this.CreateBox());
24.         }
25.  
26.         list = new List<int>(new int[points.Length]);
27.     }
28.  
29.   IEnumerator CreateBox()
30.     {
31.         while (!isGameOver)
32.         {
33.             int boxCount = (int)GameObject.FindGameObjectsWithTag("Box").Length;
34.  
35.             if (boxCount < maxBox)
36.             {              
37.                 {
38.                     for (int j = 0; j <= points.Length; j++)
39.                     {
40.                         yield return new WaitForSeconds(createTime);
41.                         int idx = Random.Range(1, points.Length);
42.  
43.                         while (list.Contains(idx))
44.                         {                          
45.                             idx = Random.Range(1, points.Length);                          
46.                         }
47.  
48.                         list[j] = idx;
49.                         Instantiate(boxPrefab, points[idx].position, points[idx].rotation);                      
50.                         Debug.Log("j =" + j);
51.                         Debug.Log("idx = " + idx);
52.                     }
53.                 }
54.             }
55.             else
56.             {
57.                 yield return null;
58.             }
59.         }
60.     }
61. }
62.  

 

You're probably infinitely looping here:

Code (csharp):

1. while (list.Contains(idx))
2. {
3.     idx = Random.Range(1, points.Length);                        
4. }

If you run out of points, there's no way to generate a random point that's not already in the list of points, so Unity's just spinning on that while-loop forever.

If there's 10 points and maxBox is 10, a simple fix is just to include the first index in your random selection:

Code (csharp):

1. Random.Range(1, points.Length);

But if you're destroying boxes, that won't be enough; you have to return the used spots to the list of spots.

 

You're starting a co-routine which uses your "list" variable, then right after you do this:
list = new List<int>(new int[points.Length]);

i dont think you want to do that, or at least wait for your coroutine to finish as they would run side-by-side.