SubApp::extract cannot be called due to borrow checker about bevy

[alice-i-cecile]

Can you give a bit more context on why you're using this pattern? I'd like to remove sub-apps completely, and want a better sense of the advanced use cases.

[anlumo]

I have a UI system (not bevy's!) and want to display bevy views as UI views, and there might be multiples of them. There's a place in the app where I have to tell bevy to render that specific view to wgpu's queue right now (synchronously), which should be achievable by running sub_app.update();. This shouldn't render the other views, only the one I want right now (because there might be UI elements between two views).

It would be nice to have separate worlds for these views. I thought about using completely separate bevy Apps for this, but then I couldn't share entities when necessary. Also, I'd have to set up all systems for every App again and again.

[alice-i-cecile]

Okay, so pretty standard multi-world / entity partitioning stuff. Thanks!

As for this issue, please feel free to make a simple PR to expose an API to do so.

[Soulghost]

I have made a simple PR to expose an API called update_sub_app_by_label to resolve this issue, could you please verify if this is in line with our expectations?

[anlumo]

I have made a simple PR to expose an API called update_sub_app_by_label to resolve this issue, could you please verify if this is in line with our expectations?

Yes, thank you!