Make this example compile and working !

[Vrixyz]

This line causes trouble:

https://github.com/Vrixyz/testbed-callback/blob/master/src/main.rs#L77

I understand why : because physics_world is move here: https://github.com/Vrixyz/testbed-callback/blob/master/src/main.rs#L67.

But I have no idea how to fix it 😞

Thanks for your help!

13/08: Help asked at nphysics forum

[thedodd]

Hey, per my comment on Twitter:
I haven’t delved too deep into the code, but a few things come to mind:

1. Use a reference instead of passing it in by value.
2. Clone it (as someone else previously mentioned).
3. Arc it (heap allocation, but that shouldn’t be a big deal).

I’ll dig a bit deeper and comment again if those options are not viable.

[Vrixyz]

Thanks ! I tried these approaches and didn't succeed (without modifying testbed source code)

My notes on these options, correct me if I'm wrong:

• reference
  In order to pass it as reference, I would need to modify testbed source code to request nphysics2d::world::World as reference instead of taking ownership to it, correct ? (I'm not sure about this one)

Best option ? If I could pass a reference of nphysics2d::world::World to specs system but pass its ownership to testbed, that would be the best option, but I had no luck trying.

• clone
  physics_world is rather heavy, but if it happens once, the performance cost is not a concern.
  I want to modify the same instance, I don't believe nphysics2d::world::World is designed to work like that. Again, that would mean modify testbed source code to allow that.

• Arc
  That means pass Arc to specs::World, and pass Arc to testbed (or more correctly, a reference to an Arc ?). Again, modify testbed source code.
  Because I can't build an Arc that I pass to a specs::System, then pass its contained item to testbed.

Now, specs is permissive about passing an Arc or whatever, so the "constraint" remains only on testbed side, and I might be oblivious of a solution which could dodge the problem.

I'll check the source code of the testbed to see what are my options, the creator of nphysics answered with valuable informations so it might help

[Vrixyz]

The branch https://github.com/Vrixyz/testbed-callback/compare/1-reference aims to answer option 1.

As Option 1 (without touching nphysics testbed source code) is the best option in my opinion, I'll focus my effort on understanding that.

I'll create MR to discuss each options in details.