Can't override type of SerializeReference fields in prefab instances

I ran into another issue with

[SerializeReference]

. If I have such a field on a component that's used in a prefab, and I then change the type inside the that field to something else in a prefab instance (either as part of another prefab, or in the scene itself), the new type doesn't actually get saved. I think this is because Unity's serialisation format doesn't actually have a way to specify type overrides yet.

Is this a known issue? Are there any known workarounds?

With all these teething issues, I'm probably going to go back to

[SerializeField]

,

ISerializationCallbackReceiver

and type-indicating enums for now. The new feature to serialise references is really powerful, but doesn't quite feel like a first-class citizen in Unity just yet.

 

Sorry, took me a few days to make a separate Unity project for this, but I've submitted a bug report now (case 1199395).

 

It's now on the public issue tracker: https://issuetracker.unity3d.com/is...erializedreference-fields-in-prefab-instances

 

@LeonhardP can you say if there are any plans to include a default property renderer for [SerializedReference] fields? (I'm imagining something that just gives you a dropdown for all types derived from field's type and then just uses the normal property rendering for the actual value.)

 

Thanks for the quick response. That's unfortunate. The lack of a default renderer isn't a huge issue, since it's not too hard to write one yourself, but not being able to actually change the type of a field is a pretty big deal breaker for a feature that's supposed to enable polymorphic serialisation.

 

Prefab variant fields are resetted too from my testing.
Do that limitation applies to prefab variants?

 

I'm pretty sure it does, since it's just a fundamental limitation of Unity's current serialisation format.

 

This is my setup:
The interface and the implementation:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public interface IBullet
6. {
7.     void Fire();
8. }
9.  
10. public class MachineGunBullet : IBullet
11. {
12.     [SerializeField] string aName = "MachineGun bullet";
13.     void IBullet.Fire()
14.     {
15.        
16.     }
17. }
18.  
19. public class AK47Bullet : IBullet
20. {
21.     [SerializeField] string aName = "AK47 bullet";
22.     [SerializeField] GameObject particle;
23.     void IBullet.Fire()
24.     {
25.        
26.     }
27. }
28.  
29. public class ShotGunBullet : IBullet
30. {
31.     [SerializeField] string aName = "ShotGun bullet";
32.     [SerializeField] AudioClip shotSound;
33.     void IBullet.Fire()
34.     {
35.        
36.     }
37. }

And the component:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class Shooter : MonoBehaviour
6. {
7.     [SerializeReference] [SerializeReferenceButton] IBullet mainBullet;
8.     [SerializeReference] [SerializeReferenceButton] List<IBullet> bullets;
9.     // Start is called before the first frame update
10.     void Start()
11.     {
12.        
13.     }
14.  
15.     // Update is called once per frame
16.     void Update()
17.     {
18.        
19.     }
20. }
21.  

The '[SerializeReferenceButton]' comes from a plugin developed by @TextusGames. Basically it creates a button beside the field which lets you to create and add an implementation of the interface from a dropdown list of all available implementation.

The shooter is attached to a gameobject which is a prefab. The default implementation of 'mainBullet' in shooter is 'ShotGunBullet'. If I drag the prefab into scene and modify 'mainBullet' to 'AK47Bullet' from 'ShotGunBullet', I am able to do so. Then if I press play and enter playmode, the field 'mainBullet''s data does not get lost or revert into something. Even I can drag the prefab into another prefab and yet no data loss. Is the issue fixed? I am confused.

Unity version 2020.3 Mac for iOS platform.