Question Resources.UnloadUnusedAssets doesn't work as expected

// Resources.UnloadUnusedAssets doesn't work in Coroutine.

Code (CSharp):

1. using System;
2. using System.Collections;
3. using UnityEditor;
4. using UnityEngine;
5.  
6. public class TestMaterialUnload : MonoBehaviour
7. {
8.     private Renderer renderer1;
9.     private Action action;
10.     void Start()
11.     {
12.         renderer1 = GameObject.CreatePrimitive(PrimitiveType.Cube).GetComponent<Renderer>();
13.  
14.         UnLoad();
15.         UnLoadImmediate();
16.         StartCoroutine(UnLoadCoroutine());
17.     }
18.  
19.     void Update()
20.     {
21.         action?.Invoke();
22.     }
23.    
24.     private void UnLoad()
25.     {
26.         var material = Material.Instantiate(renderer1.sharedMaterial);
27.         Debug.Log("UnLoad Before: " + material); // Standard(Clone) (UnityEngine.Material)
28.         var a = Resources.UnloadUnusedAssets();
29.  
30.         a.completed += (op) =>
31.         {
32.             Debug.Log("UnLoad After: " + material); // null
33.         };
34.     }
35.    
36.     private IEnumerator UnLoadCoroutine()
37.     {
38.         var material = Material.Instantiate(renderer1.sharedMaterial);
39.         Debug.Log("UnLoadCoroutine Before: " + material); // Standard(Clone) (UnityEngine.Material)
40.         var a = Resources.UnloadUnusedAssets();
41.  
42.         a.completed += (op) =>
43.         {
44.             Debug.Log("UnLoadCoroutine After completed: " + material); // Standard(Clone) (UnityEngine.Material)
45.         };
46.        
47.         while (!a.isDone)
48.         {
49.             yield return null;
50.         }
51.  
52.         Debug.LogWarning("UnLoadCoroutine After: " + material); // Standard(Clone) (UnityEngine.Material)
53.  
54.         action = () => { Debug.LogWarning("UnLoadCoroutine action: " + material); }; // Standard(Clone) (UnityEngine.Material)
55.  
56.         action();
57.     }
58.    
59.     private void UnLoadImmediate()
60.     {
61.         var material = Material.Instantiate(renderer1.sharedMaterial);
62.         Debug.Log("UnLoadImmediate3 Before: " + material); // Standard(Clone) (UnityEngine.Material)
63.         EditorUtility.UnloadUnusedAssetsImmediate();
64.         Debug.Log("UnLoadImmediate3 After: " + material); // null
65.     }
66.    
67.    
68. }
69.  

 

I am not sure what exactly your question is, but if you want to wait for Resources.UnloadUnusedAssets to complete in a Coroutine, you could try this:

Code (CSharp):

1. private IEnumerator UnLoadCoroutine()
2.     {
3.         var material = Material.Instantiate(renderer1.sharedMaterial);
4.         Debug.Log("UnLoadCoroutine Before: " + material); // Standard(Clone) (UnityEngine.Material)
5.         yield return Resources.UnloadUnusedAssets();
6.  
7.         Debug.Log("UnLoadCoroutine After completed: " + material);
8.  
9.         action();
10.     }