Bug : GetSiblingIndex always returns zero on scene root game objects in build runtime.

I reported this bug via Unity bug reporter tool long time ago but it was never fixed.

Bug record:
http://fogbugz.unity3d.com/default.asp?653948_lhpsonb8akqhg7n7

Issue tracker:
https://issuetracker.unity3d.com/issues/getsiblingindex-always-returns-zero-in-standalone-builds

Bug description:
GetSiblingIndex always returns zero on scene root game objects in build runtime.

It's working good for parented objects.
In editor play mode runtime, it's working perfect for both root and parented objects. The only problem is in build runtime for only root objects.

Steps: (test project was included in bug record when I reported it via bug reporter tool)
1) Open the test scene in editor
2) Start the play mode and see the sibling index is 1.
3) Build the project and run it.
4) Notice the sibling index is zero which is a huge bug!!!

 

Can I get attention from a Unity Team member please?

 

Bump

 

It's been days but I couldn't get any response from the Unity Team

 

Hello... I'm talking about a serious API bug here.

 

Since you sent this a while ago, have you verified this is still reproducible in the latest patch? http://unity3d.com/unity/qa/patch-releases

 

I verified it with 4.6.1p2 but I did't see any patch note about it for the other patches. Also, my bug report record is still "open"

Do you want me to verify it on 4.6.1p4?

And, why can't I find this bug in issue tracker?

 

Yes please if you could just to make sure.

I actually had passed this on but let me give the guys another gentle prod.

 

Verified. It still exists in 4.6.1p4

 

Will I be able to see it in issue tracker soon? Because trying to track it on the forum is not so cool

 

I know Unity team is very busy but...
Can I get an update about this serious API bug?
I reported it months ago.

 

Here is the issue tracker link, you can use your bug number to search in the Issue Tracker http://issuetracker.unity3d.com/issues/getsiblingindex-always-returns-zero-in-standalone-builds

It's currently still an active bug.

 

This is a serious API bug and it's not being fixed
It's been almost a year since I reported this bug. Please give some priority to this bug..!!

http://issuetracker.unity3d.com/issues/getsiblingindex-always-returns-zero-in-standalone-builds

 

Also, SetSiblingIndex is not working for gameObjects in the root (Unity 5.2.1)

 

Can we get an update from UT please? Is there a specific reason for ignoring this very obvious API bug?

 

Done. Case 733344.

 

@karl.jones

Were you able to poke the core team about the status?

 

That's very bad to hear Yes I'm aware of the workaround which is very ugly

Btw, why would a runtime API would use editor feature by default?

 

I was greatly surprised by this behavior of GetSiblingIndex too. I think some caveat section must be added to http://docs.unity3d.com/ScriptReference/Transform.GetSiblingIndex.html

 

It's been YEARS!!!

 

It's also worth mentioning that this behaviour also breaks Unity's own Hierarchy order (or at least I suppose it's connected to it). Which means that the root order in the Hierarchy is never saved in a scene, and each time you reopen it all root parents are randomized, which is super-annoying

 

Yeah, this is pretty annoying and misleading "feature" =(
It should be mentioned in docs as editor-only feature for the scene root objects.

 

You can use own implementation:

Code (CSharp):

1. int GetSiblingIndex(Transform child, Transform parent)
2.     {
3.         for (int i = 0; i < parent.childCount; ++i)
4.         {
5.             Debug.Log(child.GetInstanceID() + " - " + parent.GetChild(i).GetInstanceID());
6.             if (child.GetInstanceID() == parent.GetChild(i).GetInstanceID())
7.                 return i;
8.         }
9.         Debug.LogWarning("Child doesn't belong to this parent.");
10.         return 0;
11.     }

 

We are talking about a bug here. Why did you think I would need a workaround for it and why did you think I can't implement it myself?

 

It's a public post for people who looking for solutions as well.
I'm sure you are a cool dude and can.

 

Hmmm… this seems not to get a fix anytime soon… my current workaround is this:

Code (CSharp):

1. [SerializeField][HideInInspector]
2. private int sceneIndex;
3.  
4. #if UNITY_EDITOR
5. void OnValidate()
6. {
7.     sceneIndex = transform.GetSiblingIndex();
8. }
9. #endif
10.  

(Put this on components that need to know the sceneIndex at runtime in builds)

 

Wow.

Just ran into this myself and I'm stunned that not only did Unity never fix it, they never even added a warning to either the documentation, or when making a build or when trying to get the sibling of root object in the editor or a build.

This is a really insidious hidden gotcha just waiting to bite you on the ass, more so since it works as expected in the editor! At the very least you should get a warning in the editor when using this on a root level transform.

This has given me massive amounts of stress as i'm up against a deadline to upload builds to the stores. At the last minute I had to make a change that required using getsiblingindex() of child transforms of the root. In the editor all was well, but my builds completely broke in weird ways and its taken a good hour or more to track it down and confirm it. Didn't help that for some reason I could make a development build for Android, so was pure luck I tried a windows build and found an error message regarding duplicate keys in a sortedList as the siblingIndex always returned zero.

 

Thanks.

Thinking about it, my preferred method to address this would be an editor check if the transform is a root object and if so produce a warning or error on use. Anything else like just updating the documentation isn't going to be much help when a developer might not realize what is causing bugs in the first place! Though it'd also like to see root level transforms just return say -1 for siblingIndex since that would be pretty clear indicator that its not supported.

 

Oh, so even in 2021 this still not fixed?

 

In issue tracker page, Unity team says:

Postponed means that the issue was either a feature request or something that requires major refactoring on our side. Since that makes the issue not actionable in the close future we choose to close it as Postponed and add it on our internal roadmaps and technical debt pages instead.

This is very sad.

 

Just tripped on this for a couple hours today (w/ 2022.1). Unity, if no one can fix it, please at least document it in both the manual and API comments.

But really, please fix it. This is a landmine, destroyer of time and souls.

 

Unity, please see @Creepgin 's suggestions above.........

 

I stumbled across the problem and implemented this workaround:

Code (CSharp):

1. public static class HierarchyHelper
2.     {
3.         /// <summary>
4.         /// In a build the sibiling index of a root object is always returned as 0.
5.         /// This methods checks if the transform is a root object, and if so, determines the correct sibling index
6.         /// and returns this instead.
7.         /// </summary>
8.         /// <param name="transform"></param>
9.         /// <returns></returns>
10.         public static int GetBuildSaveSiblingIndex(this Transform transform)
11.         {
12.             if (transform.parent != null) return transform.GetSiblingIndex();
13.             var rootGameObjectTransforms = SceneManager.GetActiveScene()
14.                 .GetRootGameObjects()
15.                 .Select(go => go.transform)
16.                 .ToArray();
17.            
18.             return Array.IndexOf(rootGameObjectTransforms, transform);
19.         }
20.     }

I just tested it on Windows Standalone...