Programação Assíncrona com Kotlin Coroutines

Transcript

1. Programação Assíncrona com Kotlin Coroutines Wellington Costa Pereira
2. Wellington Costa Pereira • +4 anos de experiência • Mestrando em Ciências da Computação • Android Leader na Resource IT Solutions • Open source <3 • Compartilhar conhecimento <3 GitHub: https://github.com/WellingtonCosta E-mail: wellington.costa128@gmail.com
4. Exemplo fun updateUserData(username: String) { val user = fetchUserFromApi(username) val repos = fetchReposFromApi(username) saveUserDataInDb(user, repos) }
5. Estilo Tradicional fun updateUserData(username: String) { val user = fetchUserFromApi(username) val repos = fetchReposFromApi(username) saveUserDataInDb(user, repos) }
6. Estilo Tradicional fun updateUserData(username: String) { val user = fetchUserFromApi(username) val repos = fetchReposFromApi(username) saveUserDataInDb(user, repos) }
7. Estilo Tradicional fun updateUserData(username: String) { val user = fetchUserFromApi(username) val repos = fetchReposFromApi(username) saveUserDataInDb(user, repos) }
8. Callbacks to the rescue
9. Callback fun updateUserData(username: String) { fetchUserFromApi(username) { user -> fetchReposFromApi(username) { repos -> saveUserDataInDb(user, repos) } } }
10. Callback fun updateUserData(username: String) { fetchUserFromApi(username) { user -> fetchReposFromApi(username) { repos -> saveUserDataInDb(user, repos) } } }
11. Coroutines to the rescue
12. Coroutines suspend fun updateUserData(username: String) { val user = fetchUserFromApi(username) val repos = fetchReposFromApi(username) saveUserDataInDb(user, repos) }
13. Coroutines suspend fun updateUserData(username: String) { val user = fetchUserFromApi(username) val repos = fetchReposFromApi(username) saveUserDataInDb(user, repos) }
15. Principais Conceitos
16. Principais Conceitos • Modificador suspend • launch vs async • Dispatchers • withContext • coroutineScope • runBlocking
17. Modificador suspend A suspending function is simply a function that can be paused and resumed at a later time. They can execute a long running operation and wait for it to complete without blocking.
18. Modificador suspend suspend fun updateUserData(username: String) { val user = fetchUserFromApi(username) val repos = fetchReposFromApi(username) saveUserDataInDb(user, repos) }
19. launch vs async launch: A background job. Conceptually, a job is a cancellable thing with a life-cycle that culminates in its completion. It returns a Job instance. async: Deferred value is a non-blocking cancellable future. It’s a Job that has a result. It returns a Deferred instance.
20. launch vs async fun doSomething() { launch { // do some operation } }
21. launch vs async private val jobs = ArrayList<Job>() fun doSomething() { jobs.add( launch { // do some operation } ) } override fun onCleared() { jobs.forEach { if(!it.isCancelled) it.cancel() } }
22. launch vs async fun doSomething() { async { // do some operation } }
23. launch vs async fun doSomething() { val deferred = async { // do some operation } val result = deferred.await() }
24. launch vs async fun doSomething() { val result = async { // do some operation }.await() }
25. Dispatchers • Dispatchers.Main: A coroutine dispatcher that is confined to the Main thread operating with UI objects. • Dispatchers.Default: A coroutine dispatcher to execute CPU-bound tasks. • Dispatchers.IO: A coroutine dispatcher that is designed for offloading blocking IO tasks to a shared pool of threads.
26. withContext Calls the suspending block with a given coroutine context, suspends until it completes and then returns the result.
27. withContext suspend fun updateUserData(username: String) { withContext(Dispatchers.IO) { val user = fetchUserFromApi(username) val repos = fetchReposFromApi(username) saveUserDataInDb(user, repos) } }
28. withContext suspend fun updateUserData(username: String) { withContext(Dispatchers.IO) { val user = fetchUserFromApi(username) val repos = fetchReposFromApi(username) saveUserDataInDb(user, repos) } }
29. withContext suspend fun updateUserData(username: String) { withContext(Dispatchers.IO) { val user = fetchUserFromApi(username) val repos = fetchReposFromApi(username) saveUserDataInDb(user, repos) } }
30. coroutineScope This function is designed for a parallel decomposition of work. When any child coroutine in this scope fails, this scope fails and all the rest of the children are cancelled.
31. coroutineScope suspend fun processPayments(): List<Payment> { coroutineScope { val payments = withContext(Dispatchers.IO) { async { loadPayments() } } val processedPayments = withContext(Dispatchers.Default) { async { calculateInterestRate(payments.await()) } } return processedPayments.await() } }
32. runBlocking Runs new coroutine and blocks current thread until its completion.
33. runBlocking suspend fun processPayments(): List<Payment> { // load payments and calculate its interest rate } @Test fun myAwesomeTest() { val payments = processPayments() // assert payments interest rate }
34. runBlocking suspend fun processPayments(): List<Payment> { // load payments and calculate its interest rate } @Test fun myAwesomeTest() = runBlocking { val payments = processPayments() // assert payments interest rate }
35. Perguntas?
37. Obrigado!