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Reduce dependency on Rx with Kotlin Coroutines
This document discusses replacing RxJava with Kotlin Coroutines for asynchronous programming. It provides an overview of RxJava and Coroutines, compares their approaches, and shows how to write asynchronous code using Coroutines instead of RxJava. It also discusses how to integrate Coroutines with Retrofit and the MVVM pattern.
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Reduce dependency on Rx with Kotlin Coroutines
- 1. Reduce dependency on Rx withKotlin Coroutines LINE Fukuoka @umakoz 2019 1 23 LINE Developer Meetup #49 in KYOTO
- 2. About me • LINEFukuoka 3 • • @umakoz • LINE Creators Studio for Android • ! 3°02'03"
- 3. LINE Creators Studio •LINE • • https://creator.line.me/ja/studio/
- 4. inside LINE CreatorsStudio • Pure Kotlin without Library • MVVM • RxJava2, RxKotlin, RxLifecycle, Retrofit2, Realm...
- 5. Rx ReactiveX Reactive Extensions An APIfor asynchronous programming with observable streams.
- 6. Rx • Create Easily createevent streams or data streams. • Combine Compose and transform streams with query-like operators. • Listen Subscribe to any observable stream to perform side effects.
- 7.
- 8. RxJava A Java VMimplementation of Reactive Extensions
- 9. RxJava event/data stream •Observable 0..N flows, no backpressure, • Flowable 0..N flows, supporting Reactive-Streams and backpressure
- 10. RxJava event/data stream •Single a flow of exactly 1 item or an error, • Completable a flow without items but only a completion or error signal, • Maybe a flow with no items, exactly one item or an error.
- 11. async code usingRxJava2 fun loadSticker(id: Int): Single<Sticker> = ... loadSticker(id) .subscribeOn(Schedulers.io()) .observeOn(AndroidSchedulers.mainThread()) .subscribe( { sticker -> show(sticker) }, { error -> showError(error) } )
- 12. difficulty of Rx • •Functional Programming • Reactive Programming • operator http://reactivex.io/documentation/operators.html • Hot / Cold •
- 13.
- 14.
- 15. async code usingCoroutines suspend fun loadSticker(id: Int): Sticker = ... GlobalScope.launch(Dispatchers.Main) { try { val sticker = async(Dispatchers.IO) { loadSticker(id) }.await() show(sticker) } catch (error: Exception) { showError(error) } }
- 16. Coroutine scope A fundamentalbuilding block of coroutines. • threading • life-cycle object GlobalScope : CoroutineScope
- 17. Coroutine builder Starts coroutinefrom a regular non-suspending scope. fun CoroutineScope.launch( context: CoroutineContext = EmptyCoroutineContext, start: CoroutineStart = CoroutineStart.DEFAULT, block: suspend CoroutineScope.() -> Unit ): Job fun <T> CoroutineScope.async( context: CoroutineContext = EmptyCoroutineContext, start: CoroutineStart = CoroutineStart.DEFAULT, block: suspend CoroutineScope.() -> T ): Deferred<T>
- 18. Coroutine dispatcher Ensures thatthe execution of a coroutine gets dispatched on the right thread. • Dispatchers.Main • Dispatchers.Default • Dispatchers.IO • Dispatchers.Unconfined
- 19. suspend function Suspends executionof the code without blocking the current thread of execution. suspend fun loadSticker(id: Int): Sticker = ...
- 20. async code usingCoroutines suspend fun loadSticker(id: Int): Sticker = ... GlobalScope.launch(Dispatchers.Main) { try { val sticker = async(Dispatchers.IO) { loadSticker(id) }.await() show(sticker) } catch (error: Exception) { showError(error) } }
- 21. Compare RxJava2 streamwith Coroutines RxJava2 Coroutines Observable ReceiveChannel (experimental) Flowable ReceiveChannel (experimental) Single Deferred Completable Job Maybe Deferred
- 22. kotlinx-coroutines-rx2 • Modules thatprovide builders and iteration support for various reactive streams libraries: • Reactive Streams, RxJava 2.x, and Project Reactor https://github.com/Kotlin/kotlinx.coroutines/blob/master/ reactive/kotlinx-coroutines-rx2
- 23. RxJava2 to Coroutines suspendfun <T> SingleSource<T>.await(): T suspend fun CompletableSource.await(): Unit suspend fun <T> MaybeSource<T>.await(): T?
- 24. Coroutines to RxJava2 funCoroutineScope.rxSingle(...): Single fun CoroutineScope.rxCompletable(...): Completable fun CoroutineScope.rxMaybe(...): Maybe
- 25. How to useCoroutines on MVVM
- 26. retrofit2-kotlin-coroutines-adapter A Retrofit 2CallAdapter.Factory for RxJava2's Single. interface MyService { @GET("/sticker") fun loadSticker(id: Int): Single<Sticker> }
- 27. retrofit2-kotlin-coroutines-adapter A Retrofit 2CallAdapter.Factory for Kotlin coroutine's Deferred. interface MyService { @GET("/sticker") fun loadSticker(id: Int): Deferred<Sticker> } https://github.com/JakeWharton/retrofit2-kotlin-coroutines- adapter
- 28. Conclusion • Coroutines • RxJava2Coroutines • Coroutine Channel experimental • API DB Coroutines • View Rx Observable operator
- 29.