Better Async with Kotlin Coroutines

This talk will highlight the benefits to using coroutines over other solutions to do asynchronous programming with Kotlin on Android. The talk would also introduce how to use kotlin coroutines in our apps.

Transcript

1. Better Async with Kotlin Coroutines
2. @aditlal Adit Lal Product Engineer @vrushaliraut122 Vrushali Raut Product Engineer
3. Problem statement @WorkerThread fun loadWeather(city: String): List<Weather> { … } @MainThread fun showWeather(weather: List<Weather>) { … }
4. Thread { code } .start() object MyTask: AsyncTask() { override fun doInBackground { code } override fun onPostExecute { code } } Current Callbacks
5. Observable.from(dataSet) .map { code } .subscribe( { onNext }, { onError } ) Callbacks Current
6. Rx Solution weatherAPIService.getWeather(city="Bengaluru") .subscribeOn(io()) .observeOn(mainThread()) .subscribe ( { weatherResult -> showWeather(weatherResult) },{throwable-> handleError(throwable) })
7. What we need load { loadWeather(“Bengaluru”) } thenOnUI { showWeather(it) }
8. Corountines It can be thought of as an instance of suspend-able computation non-blocking code Coroutines simplify asynchronous programming by providing possibility to write code in direct style (sequentially).
9. “Truth can only be found in one place: the code”
10. Coroutine Example launch { println("CR start : ${getThreadName()}") Thread.sleep(100) println("CR ended : ${getThreadName()}") } run { println("Run start: ${getThreadName()}") Thread.sleep(300) println("Run ended: ${getThreadName()}") } fun funExperiment() { }
11. Run start: main CR start : commonPool-worker-1 Output Coroutine Example launch { println("CR start : ${getThreadName()}") Thread.sleep(100) println("CR ended : ${getThreadName()}") } run { println("Run start: ${getThreadName()}") Thread.sleep(300) println("Run ended: ${getThreadName()}") } fun funExperiment() { }
12. CR ended : commonPool-worker-1 Run ended: main Output Coroutine Example launch { println("CR start : ${getThreadName()}") Thread.sleep(100) println("CR ended : ${getThreadName()}") } run { println("Run start: ${getThreadName()}") Thread.sleep(300) println("Run ended: ${getThreadName()}") } } Run start: main CR start : commonPool-worker-1 fun funExperiment() {
13. Blocking Thread Time Function A Blocked Blocked Function B
14. Suspended fun Thread Time Function A Suspended Function B
15. Components Continuation Coroutine Builders Suspend functions Coroutine Context
16. Continuation Coroutine Builders Suspend functions Coroutine Context Components
17. interface Continuation<in T> { val context: CoroutineContext fun resume(value: T) fun resumeWithException(exception: Throwable) } Continuation Components
18. Components Continuation Coroutine Builders Suspend functions Coroutine Context
19. T withContext() Job launch() Deferred async() Returns result Uncaught exception - crash Fire and forget Uncaught exception - crash Non-Blocking future Uncaught exception - returned inside deferred Components
20. public actual fun launch( context: CoroutineContext = DefaultDispatcher, start: CoroutineStart = CoroutineStart.DEFAULT, parent: Job? = null, block: suspend CoroutineScope.() -> Unit ): Job Builders
21. public actual fun launch( context: CoroutineContext = DefaultDispatcher, start: CoroutineStart = CoroutineStart.DEFAULT, parent: Job? = null, block: suspend CoroutineScope.() -> Unit ): Job Builders
22. public actual fun launch( context: CoroutineContext = DefaultDispatcher, start: CoroutineStart = CoroutineStart.DEFAULT, parent: Job? = null, block: suspend CoroutineScope.() -> Unit ): Job Builders
23. public actual fun launch( context: CoroutineContext = DefaultDispatcher, start: CoroutineStart = CoroutineStart.DEFAULT, parent: Job? = null, block: suspend CoroutineScope.() -> Unit ): Job Builders
24. public actual fun launch( context: CoroutineContext = DefaultDispatcher, start: CoroutineStart = CoroutineStart.DEFAULT, parent: Job? = null, block: suspend CoroutineScope.() -> Unit ): Job Builders
25. public actual fun launch( context: CoroutineContext = DefaultDispatcher, start: CoroutineStart = CoroutineStart.DEFAULT, parent: Job? = null, block: suspend CoroutineScope.() -> Unit ): Job Builders
26. Components Continuation Coroutine Builders Suspend functions Coroutine Context
27. Suspend fun loadWeather(): Result fun loadWeather(listener: Continuation<Result>) suspend Transforms to
28. Components Continuation Coroutine Builders Suspend functions Coroutine Context
29. val uiContext: CoroutineContext = UI val bgContext: CoroutineContext = CommonPool Context
30. The plan 1. start coroutine 2. var apiData = fetchDataFromServer().await() 3. var result = parseData(apiData).await() 4. displayInList(data) 5. DSL
31. launch(context = bgContext) { val weatherResult = loadWeather("Bengaluru") } API
32. Coroutine context API launch(context = bgContext) { val weatherResult = loadWeather("Bengaluru") }
33. Coroutine builder launch(context = bgContext) { val weatherResult = loadWeather("Bengaluru") } Coroutine context API
34. val job = launch(context = CommonPool) { val weatherResult = loadWeather("Bengaluru") launch(context = UI) { showWeather(weatherResult) } } API and then show results
35. Another Coroutine API and then show results val job = launch(context = CommonPool) { val weatherResult = loadWeather("Bengaluru") launch(context = UI) { showWeather(weatherResult) } }
36. job.cancel() //cancels the execution of parent and child coroutines val job = launch(context = CommonPool) { val weatherResult = loadWeather("Bengaluru") launch(context = UI) { showWeather(weatherResult) } } API and then show results
37. • Simpler thread switching • Simple DSL • Dancing with final code Coroutines The Fun Solution
38. Solution fun getWeather(city="Bengaluru") { async(context = UI) { view.showLoading() val result = withContext(bgContext) { loadWeather(city) } showWeather(result) } }
39. Solution fun getWeather(city="Bengaluru") { launch(context = UI) { view.showLoading() val result = withContext(bgContext) { loadWeather(city) } showWeather(result) } }
40. Solution fun getWeather(city="Bengaluru") { launch(context = UI) { view.showLoading() val result = withContext(bgContext) { loadWeather(city) } showWeather(result) } }
41. Solution fun getWeather(city="Bengaluru") { launch(context = UI) { view.showLoading() val result = withContext(bgContext) { loadWeather(city) } showWeather(result) } }
42. suspend fun loadWeather (city="Bengaluru") { dataRepository.loadweather(city) } fun showWeather(weatherResult: List<WeatherResult>) { view.showWeather(weatherResult) } Solution
43. Where we were @WorkerThread fun loadWeather(city: String): List<Weather> { … } @MainThread fun showWeather(weather: List<Weather>) { … }
44. Solution fun getWeather(city="Bengaluru") { launch(context = UI) { view.showLoading() val result = withContext(bgContext) { loadWeather(city) } showWeather(result) } }
45. Fun DSL’s suspend fun <T> load(block: () -> T): Deferred<T> { } return block() fun <T> Deferred<T>.thenOnUI(uiFunction: (T) -> Unit) { } launch(UI) { uiFunction(this@thenOnUI.await()) }
46. Let’s Dance load { loadWeather(“Bengaluru”) } thenOnUI { showWeather(it) }
47. Handling exceptions
48. Stable
49. Resources try.kotlinlang.org kotlinresources.com github.com/Kotlin/kotlin-coroutines bit.ly/CodeLabCoroutines bit.ly/CoroutinesSourceDive bit.ly/CoroutinesAndroid
50. bit.ly/DevFest18Coroutines @aditlal Adit Lal @vrushaliraut122 Vrushali Raut Thats all folks!