What’s the best way to use `IO.parMapN` such that ...

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[kyleg]

What’s the best way to use IO.parMapN such that I jump back into a differnet coroutinecontext after the parallel operations have completed?

IO.parMapN(IOThread, someIO, anotherIO) { a, b ->
  continueOn(MainThread)
  // do stuff
}

Does not appear I can call continueOn inside parMapN. I tried IO.parMapN(…).continueOn(MainThread) but that doesn’t seem to actually switch me correctly. I actually have

ReaderT { 
  ... IO.parMapN(IOThread, ...).continueOn(MainThread)
}.run(context).fix().unsafeRunAsync {
  it.fold({}, { myLiveData.value = it })
}

and Android throws, telling me I can’t call setValue from a background thread.

So the continueOn doesn’t seem to change the coroutine context back to the main thread that way.

[kyleg]

Because the first IO in parMapN is just a IO-wrapped suspend function call, I have currently re-written it so that now I have

IO.parMapN(MainThread, FormerlyIOWrappedSuspend, ...) { ... }

fun FormerlyIOWrappedSuspend() = IO.fx {
  continueOn(IOThread)
  val rv = effect { suspendFn() }.bind()
  continueOn(MainThread)
  rv
}