Bug GetOrAddComponent return null, Unity 2022.3.6f1

Hello,

I am trying to get a component from a game object and if it does not exist so create it. To do so, I am using the GetOrAddComponent method but it returns a null value:

Code (CSharp):

1. gameObject.GetOrAddComponent<MeshFilter>().sharedMesh = mesh;

I have a null instance error.

Code (CSharp):

1. Debug.Log(gameObject.GetOrAddComponent<MeshFilter>());
2.  
3. // Debug:
4. // Null

 

This does not seem to be an official Unity API method according to the scripting manual for 2022.3.
I did write a method with that exact name as an extension method for my own purposes. So I assume yours is also an extension method but one with a bug.

Check the code for that method, the IDE should have something like "Go to Definition" when you right-click on the method name. Feel free to post the method here if you don't see any issues with it.

 

I've seen this exact extension method name in a few modding API's when modding Unity games, namely Subnautica. Are you modding games here?

If so you should talk to the communities behind these API's.

 

To be fair, this extension method exists probably countless of times. Here's one gist I think I even made a similar one some time ago. Though since we don't know what implementation he's actually dealing with it just makes things more complicated. So maybe this extension method has some issues or it's a timing issue. For example destroying an old MeshFilter instance and using that method within the same frame might return that dead instance. It's hard to tell without more information.

 

Hello thank you for your answers.

Here is the code of the method:

Code (CSharp):

1. public static T GetOrAddComponent<T>(this UnityObject uo) where T : Component
2. {
3.     return uo.GetComponent<T>() ?? uo.AddComponent<T>();
4. }

This is taking part of the following file:



I did my own function too:

Code (CSharp):

1. using UnityEngine;
2. using Unity.VisualScripting;
3.  
4. public static class ObjectExtensions {
5.  
6.     public static T GetComponentOrAdd<T>(this Object obj) where T : Component
7.     {
8.         T component = obj.GetComponent<T>();
9.         if (component != null)
10.             return component;
11.         else
12.             return obj.AddComponent<T>();
13.     }
14. }

 

Well, this wrong implementation IS the actual issue. Where do you got that from? This doesn't work when testing in the editor because GetComponent will return a fake null object in case the component doesn't exist. Fake null objects are not true null therefore the ?? operator can't detect it. However Unity's overloaded == operator could. Though in this case it makes much more sense to use TryGetComponent.

This should work:

Code (CSharp):

1.     return uo.TryGetComponent(out T val)?val:uo.AddComponent<T>();