Question Can't access contents of VS List in C# script

Hello!

I have an AotList scene variable tracking a set of booleans in my visual script that I want to access in a C# script, but attempting to pull that list into a C# script is giving me the error:

InvalidCastException: Specified cast is not valid.

Here's the problem code. The error is on the line defining nodeMap in the Start function:

Code (CSharp):

1. private List<bool> nodeMap = new List <bool>();
2.  
3. void Start ()
4. {
5.  
6. nodeMap = (List<bool>)Variables.ActiveScene.Get("NodeProgressMap");
7.  

I'll add that I have

using Unity.VisualScripting

and am using other VS variables in this script successfully. I only just became familiar with the concept of casting so I don't totally know what I'm doing wrong here?

 

The code is failing because an AotList can't be directly cast to a List<bool> since it inherits from ArrayList. An ArrayList is not type-safe, it can contain any kind of object. Therefore, when you try to cast an ArrayList to List<bool>, the system does not know how to handle that operation and throws an exception.

Option #1 - use LINQ Cast:

Code (CSharp):

1. using System.Collections.Generic;
2. using Unity.VisualScripting;
3. using UnityEngine;
4. using System.Linq;
5.  
6. public class NodeMap : MonoBehaviour
7. {
8.     private List<bool> nodeMap = new();
9.  
10.     void Start()
11.     {
12.         // Retrieve the node progress map. Variables.Get always returns type object
13.         object nodeProgressMapObject = Variables.ActiveScene.Get("NodeProgressMap");
14.         // Cast the retrieved object to an AotList.
15.         AotList nodeProgressMapAotList = (AotList)nodeProgressMapObject;
16.         // Cast each element in the AotList to bool, creating a new sequence of bools.
17.         IEnumerable<bool> nodeProgressMapEnumerable = nodeProgressMapAotList.Cast<bool>();
18.         // Create a new list of bools from the enumerable.
19.         nodeMap = new List<bool>(nodeProgressMapEnumerable);
20.     }
21. }

The above step-by-step process can be summarized in this single line of code:

Code (CSharp):

1. nodeMap = new List<bool>(((AotList)Variables.ActiveScene.Get("NodeProgressMap")).Cast<bool>());

Option #2 - foreach loop. If the collection is relatively small and is not processed every frame, then LINQ is fine. But if you need a more performant version without LINQ's allocations, then you can also do it the old-fashioned way:

Code (CSharp):

1. using System.Collections.Generic;
2. using Unity.VisualScripting;
3. using UnityEngine;
4.  
5. public class NodeMap : MonoBehaviour
6. {
7.     private List<bool> nodeMap = new();
8.  
9.     void Start()
10.     {
11.         var nodeProgressMap = (AotList)Variables.ActiveScene.Get("NodeProgressMap");
12.         foreach (var node in nodeProgressMap)
13.         {
14.             nodeMap.Add((bool)node);
15.         }
16.     }
17. }

 

@PanthenEye Thank you so much! The "old fashioned" approach was exactly what I needed. I didn't realize that the C# var and the Get call to the VS var would use their respective types. I had tried changing both to list, and both to AotList, but not mixing the two.

 

@PanthenEye I have this script attached to my enemies. I get the aotlist cast it to the new list and then set it. It seems to only work with a single enemy if there are more I get an error. Do you know a solution to this?


InvalidCastException: Specified cast is not valid.
EnemyBehavior.DestroyGameObject () (at Assets/Levels/Gameplay/Enemy/EnemyBehavior.cs:38)
EnemyBehavior.Update () (at Assets/Levels/Gameplay/Enemy/EnemyBehavior.cs:80)

Code (CSharp):

1. using System;
2. using System.Collections;
3. using UnityEngine;
4. using Unity.VisualScripting;
5. using System.Linq;
6. using System.Collections.Generic;
7. using UnityEngine.UI;
8.  
9.  
10. public class EnemyBehavior :MonoBehaviour
11. {
12.  
13.     //public GameObject SceneVariables;
14.  
15.     public int EnemyHealth;
16.     public Vector3 PointA;
17.     public int MaxLimit;
18.     public int MinLimit;
19.     int x = 1;
20.  
21.  
22.     public bool EnemyDestroyed = false;
23.  
24.     private List<Image> nodeMap = new();
25.  
26.     private List<GameObject> Enemylist = new();
27.  
28.  
29.     public void DamageEnemy(int damage)
30.     {
31.  
32.         EnemyHealth = EnemyHealth - damage;
33.  
34.     }
35.     public void DestroyGameObject()
36.     {
37.  
38.          Enemylist = new List<GameObject>(((AotList)Variables.ActiveScene.Get("EnemyList")).Cast<GameObject>());
39.          nodeMap = new List<Image>(((AotList)Variables.ActiveScene.Get("EnemyPositionCamera")).Cast<Image>());
40.  
41.  
42.  
43.         Destroy(nodeMap[Enemylist.IndexOf(gameObject)]);
44.         nodeMap.RemoveAt(Enemylist.IndexOf(gameObject));
45.  
46.  
47.  
48.         Enemylist.Remove(gameObject);
49.  
50.  
51.  
52.         Variables.ActiveScene.Set("EnemyList", Enemylist);
53.  
54.         Variables.ActiveScene.Set("EnemyPositionCamera",nodeMap);
55.  
56.  
57.  
58.         //EnemyDestroyed = true;
59.          Destroy(gameObject);
60.        
61.     }
62.  
63.     void Start()
64.     {
65.  
66.  
67.  
68.  
69.  
70.     }
71.  
72.     void Update()
73.     {
74.        
75.  
76.         //Debug.Log(Enemylist.Count);
77.  
78.         if (EnemyHealth < 1 && gameObject == true)
79.         {
80.             DestroyGameObject();
81.         }
82.  
83.        
84.  
85.        // Debug.Log(nodeMap.Count);
86.         //Debug.Log(Enemylist.IndexOf(gameObject));
87.  
88.  
89.  
90.  
91.         transform.Translate(PointA * Time.deltaTime * x);
92.  
93.  
94.         if(transform.position.x > MaxLimit )
95.         {
96.  
97.  
98.             x = -1;
99.  
100.  
101.         }
102.  
103.  
104.  
105.         if (transform.position.x < MinLimit)
106.         {
107.  
108.  
109.             x = 1;
110.  
111.  
112.         }
113.  
114.  
115.  
116.     }
117.  
118.  
119.  
120.  
121.  
122. }
123.  

 

First, make sure that the objects you're getting from Variables.ActiveScene.Get("EnemyList") and Variables.ActiveScene.Get("EnemyPositionCamera") are indeed of type AotList.

Secondly, check the items inside the AotList: Even if the outer list is of type AotList, the elements inside might not be of the expected type. You have to ensure that every element inside Variables.ActiveScene.Get("EnemyList") is a GameObject and every element inside Variables.ActiveScene.Get("EnemyPositionCamera") is an Image.

Thridly, it might be a good idea to separate the concerns. Add an EnemyManager script that adds and removes from the enemy lists. A single enemy shouldn't have access to other enemy data unless necessary for AI or similar utility in which case it could still communicate with EnemyManager.

EDIT: Also, "gameobject == true" in your Update() function is not a valid syntax. Use "gameObject.activeSelf" instead.