If people are interested in starting `arrow-androi...

# arrow

[simon.vergauwen]

If people are interested in starting arrow-android we’d love to help people get started with any help they need 🙂

[dcampogiani]

Do you have some use case in mind?

[simon.vergauwen]

A great first step would be an integration between IO and the Android’s Lifecycle I think.

Which we should be able to easily refactor to F later on.

[thanh]

Sounds interesting! I'm using MVI with Rxbinding. Can I replace Rxjava with IO in my case?

[simon.vergauwen]

If you’re using Observable or Flowable than I wouldn’t recommend it.

[simon.vergauwen]

You could rewrite to IO but RxJava’s types are already “functional types”. You can also use them with Arrow Fx and with the principled APIs of Arrow.

[simon.vergauwen]

When dealing with such situations I typically have Rx in the Fragment/Activity which I bind with autodipose since I only have a single stream in onResume (99% of the time).

[simon.vergauwen]

flatMapIO is currently missing from the ObservableK and FlowableK API however.

[thanh]

thanks Simon, that's what I'm doing now.

[simon.vergauwen]

Nice! Only additional thing I’ve considered is doing IO and suspend in the non-android layers so I could have MPP support by the end of the year.

[thanh]

for Rxbinding usecase, do you have any way rewrite it in a more functional way? So we can have easy support for Coroutines channels, rxjava, etc

[simon.vergauwen]

You have an example? Not sure I understood the question correctly

[thanh]

I'm working on a bluetooth library, so I need to provide a stream of state of a bluetooth device. I'm heavily using Rxjava now. I want to provide more safe and general solution with Arrow.

[simon.vergauwen]

You can use arrow-fx-rx integration which opens up safe combinators for Rx such as bracketCase etc

[simon.vergauwen]

It exposes the exact same API as IO but for Rx

[simon.vergauwen]

I want to provide more safe and general solution with Arrow.

If you want to replace Rx with IO you can rely on recursion with IO but I’d recommend sticking with Rx until arrow-streams becomes available.

[simon.vergauwen]

Using Rx with arrow-fx-rx should give you similar guarantees, and since it’s Android specific you’re already tied to the JVM anyway.

[dcampogiani]

to bind effects to Android Lifecycle the setTagIfAbsent could be useful

[dcampogiani]

https://android-review.googlesource.com/c/platform/frameworks/support/+/772083/9/lifecycle/viewmodel/ktx/src/main/java/androidx/lifecycle/ViewModel.kt#40

[dcampogiani]

this way you get automatic cancel/close in the viewmodel, without manual cancel

[simon.vergauwen]

Oh very interesting, I didn’t know about that one. That would be super awesome to have!

[dcampogiani]

The problem is that API isn’t really public…

[carbaj0]

Another way of manage lifecycle could be with LifecycleObservers

This is an example for manage when the app goes to foreground

[simon.vergauwen]

You can integrate with Android Lifecycle using this combinator.

fun <A> IOOf<A>.unsafeRunScoped(owner: LifecycleOwner, cancelAt: Lifecycle.Event = Lifecycle.Event.ON_STOP, f: (Either<Throwable, A>) -> Unit): Unit =
  if (owner.lifecycle.currentState == Lifecycle.State.DESTROYED) Unit
  else {
    val disposable = fix().unsafeRunAsyncCancellable(cb = f)

    owner.lifecycle.addObserver(object : LifecycleEventObserver {
      override fun onStateChanged(source: LifecycleOwner, event: Lifecycle.Event) {
        if (event == cancelAt) disposable.invoke()
      }
    })
  }