Better Async With Kotlin Coroutines

In this talk we explained how coroutines allow running an asynchronous piece of code in the same manner as you’d normally run a synchronous one. We also explained here about coroutine component, builders and other many important concepts. We have explain it real life examples.

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 } ) Current Callbacks
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. 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() { } Run start: main CR start : commonPool-worker-1 Output
12. 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() { } Run start: main CR start : commonPool-worker-1 Output CR ended : commonPool-worker-1 Run ended: main
13. Coroutine Example runBlocking { launch(coroutineContext) { 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() { }
14. Coroutine Example runBlocking { launch(coroutineContext) { 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() { }
15. Coroutine Example runBlocking { launch(coroutineContext) { 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() { } Run start: commonPool-worker-1 Run ended: commonPool-worker-1 CR start : commonPool-worker-1 CR ended : commonPool-worker-1 Output
16. Blocking Thread Time Function A Blocked Blocked Function B
17. Suspended fun Thread Time Function A Suspended Function B
18. Components Continuation Coroutine Builders Suspend functions Coroutine Context
19. Components Continuation Coroutine Builders Suspend functions Coroutine Context
20. interface Continuation<in T> { val context: CoroutineContext fun resume(value: T) fun resumeWithException(exception: Throwable) } Continuation Components
21. Components Continuation Coroutine Builders Suspend functions Coroutine Context
22. T Components withContext() Job launch() Deferred async() Returns result Uncaught exception - crash Fire and forget Uncaught exception - crash Non-Blocking future Uncaught exception - returned inside deferred
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. public actual fun launch( context: CoroutineContext = DefaultDispatcher, start: CoroutineStart = CoroutineStart.DEFAULT, parent: Job? = null, block: suspend CoroutineScope.() -> Unit ): Job Builders
27. public actual fun launch( context: CoroutineContext = DefaultDispatcher, start: CoroutineStart = CoroutineStart.DEFAULT, parent: Job? = null, block: suspend CoroutineScope.() -> Unit ): Job Builders
28. public actual fun launch( context: CoroutineContext = DefaultDispatcher, start: CoroutineStart = CoroutineStart.DEFAULT, parent: Job? = null, block: suspend CoroutineScope.() -> Unit ): Job Builders
29. Components Continuation Coroutine Builders Suspend functions Coroutine Context
30. Suspend fun loadWeather(): Result fun loadWeather(listener: Continuation<Result>) suspend Transforms to
31. Components Continuation Coroutine Builders Suspend functions Coroutine Context
32. val uiContext: CoroutineContext = UI val bgContext: CoroutineContext = CommonPool Context
33. The plan 1. start coroutine 2. var apiData = fetchDataFromServer().await() 3. var result = parseData(apiData).await() 4. displayInList(data)
34. launch(context = bgContext) { val weatherResult = loadWeather("Bengaluru") } Builders
35. launch(context = bgContext) { val weatherResult = loadWeather("Bengaluru") } Coroutine context Builders
36. launch(context = bgContext) { val weatherResult = loadWeather("Bengaluru") } Coroutine builder Coroutine context Builders
37. val job = launch(context = CommonPool) { val weatherResult = loadWeather("Bengaluru") launch(context = UI) { showWeather(weatherResult) } } Solution 1
38. val job = launch(context = CommonPool) { val weatherResult = loadWeather("Bengaluru") launch(context = UI) { showWeather(weatherResult) } } Another Coroutine Solution 1
39. Solution 1 job.cancel() val job = launch(context = CommonPool) { val weatherResult = loadWeather("Bengaluru") launch(context = UI) { showWeather(weatherResult) } }
40. • Simpler thread switching • Simple DSL • Dancing with final code Coroutines The fun Solution
41. Solution fun getWeather(city="Bengaluru") { async(context = UI) { view.showLoading() val result = withContext(bgContext) { loadWeather(city) } showWeather(result) } }
42. Solution fun getWeather(city="Bengaluru") { async(context = UI) { view.showLoading() val result = withContext(bgContext) { loadWeather(city) } showWeather(result) } }
43. fun getWeather(city="Bengaluru") { async(context = UI) { view.showLoading() val result = withContext(bgContext) { loadWeather(city) } showWeather(result) } } Solution
44. Solution fun getWeather(city="Bengaluru") { async(context = UI) { view.showLoading() val result = withContext(bgContext) { loadWeather(city) } showWeather(result) } }
45. Solution suspend fun loadWeather (city="Bengaluru") { dataRepository.loadweather(city) } fun showWeather(weatherResult: List<WeatherResult>) { view.showWeather(weatherResult) }
46. Where we were @WorkerThread fun loadWeather(city: String): List<Weather> { … } @MainThread fun showWeather(weather: List<Weather>) { … }
47. 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@then.await()) }
48. Let’s Dance load { loadWeather(“Bengaluru”) } thenOnUI { showWeather(it) }
49. Resources https://try.kotlinlang.org https://www.kotlinresources.com https://github.com/Kotlin/kotlin-coroutines http://bit.ly/CodeLabCoroutines http://bit.ly/CoroutinesSourceDive http://bit.ly/CoroutinesAndroid
50. Thank you Questions http://bit.ly/DevFest18Coroutines @aditlal Adit Lal @vrushaliraut122 Vrushali Raut