Better Async With Kotlin Coroutines

Better Async With Kotlin Coroutines @ Kotlin Night Torino 2018

Transcript

1. Better Async with context() Kotlin Coroutines Leonardo Pirro Android Developer @ IQUII @lpirro93
2. Who Am I? Hi, I’m Leo. Android Developer @ IQUII
3. Why Coroutines? Coroutines simplify asynchronous programming by providing a set of APIs to write code in direct style (sequentially)
4. Why Coroutines? • Asynchronous programming is becoming really important for developers • The other tools that we have today introduced a lot of complexity • Callback Hell
6. What we have now Thread { code } .start() object MyAsyncTask: AsyncTask() { override fun doInBackground { code } override fun onPostExcecute { code } } Observable.just(1,2,3,4) .map { code } .doOnEach { code } .doOnError { code } .subscribeOn( { onNext }, { onError } )
7. What we have now Thread { code } .start() object MyAsyncTask: AsyncTask() { override fun doInBackground { code } override fun onPostExcecute { code } } Observable.just(1,2,3,4) .map { code } .doOnEach { code } .doOnError { code } .subscribeOn( { onNext }, { onError } )
8. What we have now WANT fun loadNews() = launch { view.showLoading() val result = async { // computation }.await() view.hideLoading() view.showData(result) }
9. Coroutines
10. Coroutines • Introduced in Kotlin 1.1 • Experimental (but several companies, including us in IQUII, are using them in production with zero problems)
11. coroutine builder coroutine context suspend function builders to launch coroutine coroutine dispatchers mark suspention point Coroutines
12. coroutine builder builders to launch coroutine coroutine context suspend function coroutine dispatchers mark suspention point Coroutines
13. coroutine builder coroutine context suspend function builders to launch coroutine coroutine dispatchers mark suspention point Coroutines
14. coroutine builder coroutine context suspend function builders to launch coroutine coroutine dispatchers mark suspention point Coroutines
15. Coroutines - Builders withContext return result uncaught exception crashes your app T launch Job fire and forget uncaught exception crashes your app async Deferred returns non-blocking future uncaught exception is shared inside the resulting Deferred
16. Coroutines - Context coroutine context UI dispatch execution into Android main thread CommonPool dispatch execution into background thread Unconfined dispatch execution into current thread
17. Coroutines - Suspend Function suspend fun fetchNews(): News suspend function fun fetchNews(listener: Continuation<News>) Trasformed to
19. How to create a coroutine
20. How to create a coroutine fun loadPlayes() { view?.showLoading() val result = dataManager.getPlayers() view?.showPlayers(result) view?.hideLoading() }§
21. How to create a coroutine fun loadPlayes() = launch( § UI § ) { view?.showLoading() val result = dataManager.getPlayers() view?.showPlayers(result) view?.hideLoading() }§
22. How to create a coroutine Parent coroutine fun loadPlayes() = launch( § UI § ) { § view?.showLoading() val result = dataManager.getPlayers() view?.showPlayers(result) view?.hideLoading() }§
23. How to create a coroutine Result in UI Thread fun loadPlayes() = launch(UI) { § view?.showLoading() val result = dataManager.getPlayers() view?.showPlayers(result) view?.hideLoading() }§
24. How to create a coroutine fun loadPlayes() = launch(UI) { view?.showLoading() val result = dataManager.getPlayers() view?.showPlayers(result) view?.hideLoading() }§
25. How to create a coroutine fun loadPlayes() = launch(UI) { view?.showLoading() val result = withContext(CommonPool) { dataManager.getPlayers() } view?.showPlayers(result) view?.hideLoading() }§
26. How to create a coroutine fun loadPlayes() = launch(UI) { view?.showLoading() val result = withContext(CommonPool) { dataManager.getPlayers() } view?.showPlayers(result) view?.hideLoading() }§ child coroutine
27. How to create a coroutine fun loadPlayes() = launch(UI) { view?.showLoading() val result = withContext(CommonPool) { dataManager.getPlayers() } view?.showPlayers(result) view?.hideLoading() }§
28. What about cancellation?
29. Cancelling a coroutine var job: Job? = null fun onPlayerButtonClicked(){ job = loadPlayers() } fun onBackClicked(){ job?.cancel() } private fun loadPlayers() = launch(UI) { // code }
30. Cancelling a coroutine var job: Job? = null fun onPlayerButtonClicked(){ job = loadPlayers() } fun onBackClicked(){ job?.cancel() } private fun loadPlayers() = launch(UI) { // code }
31. Cancelling a coroutine var job: Job? = null fun onPlayerButtonClicked(){ job = loadPlayers() } fun onBackClicked(){ job?.cancel() } private fun loadPlayers() = launch(UI) { // code }
32. What about error handling? try { } catch(err: SlideNotFoundException) { }
33. Error handling - try/catch block fun loadPlayes() = launch(UI) { view?.showLoading() try { val result = withContext(CommonPool) { dataManager.getPlayers() view?.showPlayers(result) } catch (e: IllegalArgumentException) { // handle errors } view?.hideLoading() }
34. Error handling - Store inside Deferred fun loadPlayes() = async(UI) { view?.showLoading() val task = async(CommonPool) { dataManager.getPlayers() } val result = task.await() view?.showPlayers(result) view?.hideLoading() }
35. Error handling - Store inside Deferred var job: Deferred<*> = loadPlayes() job.invokeOnCompletion { it?.printStackTrace() }
36. Other cool stuff - Retrofit 2 Adapter interface MyApiService { @GET("user") fun getuser(): Deferred<User> // or... @GET("user") fun getuser(): Deferred<Response<User>> }
37. Setup Coroutines implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:0.22.2" implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:0.22.2" build.gradle kotlin { experimental { coroutines 'enable' } } gradle.properties kotlin.coroutines=enable
38. Link utili • Kotlin community: https://kotlinlang.org/community • Official Slack: http://slack.kotlinlang.org • Android Developers Italy: https://androiddevsitaly.slack.com • Kotlin Coroutines official guide: https://github.com/Kotlin/ kotlinx.coroutines/blob/master/coroutines-guide.md Slide of this talk: https://speakerdeck.com/lpirro
39. http://www.androiddevs.it Slack community - Android Developers Italia
40. Thank You Leonardo Pirro Android Developer @ IQUII @lpirro93