Resolved UIDocuments working unreliably + workaround

Solved: to register UIDocument events use OnEnable().


While moving my scripts from PanelRenderer + postUxmlReload api to UIDocument I discovered that mu UI isn't working well anymore. I register my events for Buttons and Sliders in Start() methods, as seen elsewhere in github repo, but they weren't working reliably (only one of UIDocument worked... for no clear reason too).
Strongly suspecting a race condition here I created a simple script:

Code (CSharp):

1. void Awake ()
2. {
3.     // workaround for UIDocument binding not working, part 1/2
4.     var arr = FindObjectsOfType<UIDocument>();
5.     foreach( var comp in arr )
6.         comp.gameObject.SetActive(false);
7. }
8.  
9. void Start ()
10. {
11.     // workaround for UIDocument binding not working, part 2/2
12.     var arr = FindObjectsOfType<UIDocument>( includeInactive:true );
13.     foreach( var comp in arr )
14.         comp.gameObject.SetActive(true);
15. }

and to my surprise - it solved the issue!
But... why?

Unity 2020.1.5f1, UI Toolking 1.0.0-preview.8

 

These samples misguided me then:
https://github.com/Unity-Technologies/UIToolkitUnityRoyaleRuntimeDemo/blob/4cba10669901b41d66aa8ab215641b1a5542791f/Assets/Scripts/UI/GameScreen.cs
But I can see now those samples aren't registering anything in Start()

 

I removed workaround, moved event registration to OnEnable and it works even better than before
Thank you @JuliaP_Unity !