C# override a destroyed GameObject in a List

Questions & Answers
1

Hello,

I try to restore already destroyed GameObjects. Therefore I created a struct which is saving the whole GameObject, the number which is written in a TextMesh “on” my GameObject and the Prefab which I used to spawn it. Then I created a List of this struct.

private struct NumObjectStruct{
		private GameObject GO;
		private int num;
		private Transform pref;
		
		public NumObjectStruct(GameObject GO, int num, Transform pref){
			this.GO = GO;
			this.num = num;
			this.pref = pref;
		}
		
		public GameObject getGO(){
			return this.GO;
		}
		
		public int getNum(){
			return this.num;
		}
		
		public Transform getPref(){
			return this.pref;
		}
		
		public void setGO(GameObject vGO){
			GO = vGO;
		}
		
		public void setNum(int vNum){
			num = vNum;
		}
		
		public void setPref(Transform vPref){
			pref = vPref;
		}
		
	}
	
	List<NumObjectStruct> SpawnedNumberObjects = new List<NumObjectStruct>();

When I generate a new number I am spawning a new GameObject.

GameObject Inst;
				Inst = (Instantiate (shownObject, spawnPos, transform.rotation) as Transform).gameObject;
			
				NumObjectStruct newStructForList = new NumObjectStruct(Inst, rndNumber, shownObject);
			
				SpawnedNumberObjects.Add (newStructForList);
				//End Spawning
			
				Transform TextMeshTransform = SpawnedNumberObjects[currentNumberInd].getGO ().transform.FindChild ("NumberText");
				TextMesh NumberText = TextMeshTransform.GetComponent(typeof(TextMesh)) as TextMesh; 
				NumberText.text = rndNumber.ToString ();

shownObject is a public Transform which I set with one of my Prefabs, spawnPos is a Vector3, rndNumber is an integer of the number I generated and currentNumberInd is an integer which I am using as counter for how many Objects are in my List. The default value of the counter is 0 and after spawning a new Object I am increasing it by one.

During my Program there will be the situation that I have to Destroy one of those objects.

void DestroyNumberObject(){
		Destroy(SpawnedNumberObjects[DestroyIndex].getGO ());	
	}

Now my problem comes:
There is the situation that I need to restore one of the GameObjects I already destroyed. Therefore I also saved my number and the prefab inside my struct. Then I instantiate it again and try to override the destroyed GameObject in the List with my new recreated GameObject.

GameObject ReSave;
							ReSave = (Instantiate (SpawnedNumberObjects[currentNumberInd-1-AnimNodeAmount].getPref().transform, spawnStornoPos, transform.rotation) as Transform).gameObject;
							print ("resave: " + ReSave);
							Transform TextMeshTransform = ReSave.transform.FindChild ("NumberText");
							TextMesh NumberText = TextMeshTransform.GetComponent(typeof(TextMesh)) as TextMesh; 
							NumberText.text = SpawnedNumberObjects[currentNumberInd-1-AnimNodeAmount].getNum ().ToString ();
					
							SpawnedNumberObjects[currentNumberInd-1-AnimNodeAmount].setGO(ReSave);
							print ("resave in list: "+SpawnedNumberObjects[currentNumberInd-1-AnimNodeAmount].getGO ());

The “AnimNodeAmount” is also an integer. This value is “4” because there are 4 Objects shown on my display. The rest in the array is either destroyed or doesn´t exist (anymore).

My Output is:

resave: NumberObjectRed(Clone) (UnityEngine.GameObject)

resave in list: null

Why is the value inside my struct null now? What am I doing wrong?

Any help is appreciated.
Thank you in advance.

2

Your problem is that you used the combination of a value type (your struct) and a List. When ever you access an element in your list you will get a copy of your struct.

This line:

SpawnedNumberObjects[currentNumberInd-1-AnimNodeAmount].setGO(ReSave);

will execute the get-method of the index-property of your List object. The getter will return a copy of your requested element. On this copy you invoke setGO.

You either have to use a class instead of your struct, so you have a reference type and you always work on the same instance, or do it like this:

NumObjectStruct tmp = SpawnedNumberObjects[currentNumberInd-1-AnimNodeAmount]; // invoke getter
tmp.setGO(ReSave); // change the temp object
SpawnedNumberObjects[currentNumberInd-1-AnimNodeAmount] = tmp; // invoke setter