[WIP] Introduce Arrow Fx

[takahirom]

Overview (Required)

• It is still not working 😭. Probably because It is not released yet.

 E/AndroidRuntime: FATAL EXCEPTION: main
    Process: io.github.droidkaigi.confsched2019.debug, PID: 14255
    kotlin.UninitializedPropertyAccessException: lateinit property retVal has not been initialized
        at arrow.typeclasses.suspended.BlockingContinuation.getRetVal(MonadSyntax.kt:24)
        at arrow.typeclasses.suspended.MonadSyntax$DefaultImpls.effect(MonadSyntax.kt:12)
        at arrow.typeclasses.MonadContinuation.effect(MonadContinuations.kt:16)
        at io.github.droidkaigi.confsched2019.session.ui.actioncreator.SessionContentsActionCreator$toggleFavorite$1.invokeSuspend(SessionContentsActionCreator.kt:71)
        at io.github.droidkaigi.confsched2019.session.ui.actioncreator.SessionContentsActionCreator$toggleFavorite$1.invoke(Unknown Source:10)
        at arrow.typeclasses.Monad$fx$wrapReturn$1.invokeSuspend(Monad.kt:80)
        at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:32)
        at kotlin.coroutines.ContinuationKt.startCoroutine(Continuation.kt:128)
        at arrow.typeclasses.Monad$DefaultImpls.fx(Monad.kt:81)
        at arrow.core.extensions.TryMonad$DefaultImpls.fx(Unknown Source:8)
        at arrow.core.extensions.try.monad.TryMonadKt$monad$1.fx(TryMonad.kt:195)
        at arrow.core.extensions.try.monad.TryMonadKt.fx(TryMonad.kt:178)
        at io.github.droidkaigi.confsched2019.session.ui.actioncreator.SessionContentsActionCreator.toggleFavorite(SessionContentsActionCreator.kt:70)
        at io.github.droidkaigi.confsched2019.session.ui.item.SpeechSessionItem$bind$$inlined$with$lambda$2.onClick(SpeechSessionItem.kt:80)
        at android.view.View.performClick(View.java:6294)
        at android.view.View$PerformClick.run(View.java:24770)
        at android.os.Handler.handleCallback(Handler.java:790)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6494)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

[jmatsu-bot]

Try it via https://deploygate.com/distributions/839c04a0bac8f01c8b99f859b728244497ec7e31

[jmatsu]

What's the purpose to use fx? 🤔
AFAIK, fx forces to represent side-effects by using suspend functions through compilation errors.

If you want to just integrate with coroutine, then arrow supports coroutine extension with DefferedK

val defferedK = async {
...
LoadingState.LOADED
}.k().handleErrorWith {
   dispatcher.dispatch(
                        Action.ShowProcessingMessage(
                            Message.of(
                                R.string.session_favorite_connection_error
                            )
                        )
                    )
  LoadingState.INITIALIZED
 }

dispatcher.dispatch(defferedK.unsafeAttemptSync())

maybe be like above.

[jmatsu]

😇
https://github.com/arrow-kt/arrow/blob/master/modules/effects/arrow-effects-kotlinx-coroutines-extensions/src/main/kotlin/arrow/effects/coroutines/extensions/deferredk.kt

[takahirom]

Yes. Probably .k and DeferredK will be removed. 😇

[jmatsu]

After diving into arrow fx, I found a cause.

The current fx is for Try monad and it doesn't take care of asynchronous operations.

In FP world, IO monad is what you need to use.

• Add io.arrow-kt:arrow-effects-io-extensions dependency
• Import arrow.effects.extensions.io.fx.fx correctly

Then, follow the style below.

fun toggleFavorite(...) {
        unsafe {
            runNonBlocking({
                fx {
                    ....
                }
            }, { // Either monad will be coming
            })
        }
}

[takahirom]

Currently, the coroutines are not canceled when coroutineContext is canceled. 😭

[jmatsu-bot]

Apk comparision results

Property	Summary
New File Size	8496751 Bytes. (8.1 MB)
File Size Change	+36259 Bytes. (+35.41 KB)
Download Size Change	+34935 Bytes. (+34.12 KB)
New Method Reference Count	63263
Method Reference Count Change	554
New Number of dex file(s)	1
Number of dex file(s) Change	0

Generated by 🚫 Danger

[jmatsu-bot]

Asserted successfully. 💯

Generated by 🚫 Danger