Add body existence check in step function

[Alexander Shortt]

Hello - something about my usage seems to be wrong and I'd love some help figuring that out, but an issue regardless of my setup is the error Cannot read properties of undefined (reading 'position') coming from this line. For some reason my body subscriptions are losing values but not disappearing from state. There should definitely be a check there . I'll submit a pr in a second.

As for what may be wrong with my setup, I'm using the Physics component in a separate component, seen here, which upon re-render may be losing internal state.

[Alexander Shortt]

Submitted a pr here: #408

As for the cause, after looking at the source I can better describe it as unloaded bodies don't seem to remove subscriptions. So it's probably not the Physics component itself that's resetting since it's still aware of the subscriptions, but that the body is being unloaded without the subscriptions being unloaded.

[Darko Petrovic]

I've the same error when using api subscription and when objects are removed from the scene. Don't know how but then the api stops working for the other objects too.

[Alexander Shortt]

yeah i can second this ^ seems to happen when objects are removed from the scene

[Bjorn Stromberg]

Could you share a reproduction with us then we can be sure to fix it.

[Alexander Shortt]

@bjornstar the problem seems clear, as pointed out here, subscriptions aren't being removed when the body is removed. am i missing something?

this is my fix in #411:

use-cannon/packages/cannon-worker-api/src/worker/index.ts

Lines 48 to 52 in 9259f87

   const key = Object.keys(state.subscriptions).find((k) => state.subscriptions[k][0] === data.uuid[i]) 
   if (key) { 
     delete state.subscriptions[key] 
   } 
 } 

[Alexander Shortt]

now fixed in #412

[Matt Black]

I experienced this when I setup a subscription but did not handle the returned unsubscribe function from subscribe.

So kids, eat your veggies and don't forget to unsub

useEffect(() => { 
  const unsub = api.subscribe(...)
  return unsub 
}, [api])

so it gets called when your component unmounts.