É abordado o tópico de programação assíncrona, focando no modo de funcionamento das Coroutines em Kotlin e como ele se diferencia das tradicionais Threads. É visualizado também casos de uso, verificando onde é mais vantajoso a aplicação de cada uma.

1. ProgramaçãoProgramação
Assíncrona comAssíncrona com
Kotlin CoroutinesKotlin Coroutines
2019

2. Lucas BorsattoLucas Borsatto

3. Async:Async:
Concorrência &Concorrência &
ParalelismoParalelismo

4. SequencialSequencial
1. CPU ociosa
2. Main Thread bloqueada
3. Congelamento do app

5. AsyncAsync

6. Exemplo:Exemplo:
Atualização de PDVsAtualização de PDVs

7. AbordagensAbordagens
1. Síncrona
2. Com Threads
3. Com Coroutines

8. SíncronoSíncrono

9. Síncrono - CódigoSíncrono - Código
fun getAmePrices() : List<Price> { ... }
fun getAmeProducts(): List<Product> { ... }
fun savePriceProductToStore(prices: List<Price>, products: List<Product>) { ... }
fun postNotificationToPOS(posId: Int) : Response { ... }
fun updatePosAssortment(posId): Response{
val prices = getAmePrices()
val products = getAmeProducts()
val savePriceAndProductToPOS(prices, products)
return postNotificationToPOS(posId)
}

10. ThreadsThreads

11. Threads - InterfaceThreads - Interface
fun thread(
start: Boolean = true,
isDaemon: Boolean = false,
contextClassLoader: ClassLoader? = null,
name: String? = null,
priority: Int = -1,
block: () -> Unit
): Thread

12. Threads - CódigoThreads - Código
fun updatePosAssortment(posId: Int): Response{
val prices = getAmePrices()
val products = getAmeProducts()
val savePriceAndProductToPOS(prices, products)
return postNotificationToPOS(posId)
}
for(pos in posList){
thread(start=true){
updatePosAssortment(pos.posId)
}
}

13. Threads - FluxoThreads - Fluxo

14. Threads - DesvantagensThreads - Desvantagens
Quanto mais threads:
1. Maior trabalho pro SO
2. Maior consumo de memória
3. Maior tempo de CPU ociosa

15. CoroutinesCoroutines

16. Coroutines - InterfaceCoroutines - Interface
fun CoroutineScope.launch(
context: CoroutineContext = EmptyCoroutineContext,
start: CoroutineStart = CoroutineStart.DEFAULT,
block: suspend CoroutineScope.() -> Unit
): Job (source)

17. Coroutines - CódigoCoroutines - Código
suspend fun getAmePrices() : List<Price> { ... }
suspend fun getAmeProducts(): List<Product> { ... }
suspend fun savePriceProductToStore(prices: List<Price>, products: List<Product>)
{ ... }
suspend fun postNotificationToPOS(posId: Int) : Response { ... }
suspend fun updatePosAssortment(posId): Response{
val prices = getAmePrices()
val products = getAmeProducts()
val savePriceProductToPOS(prices, products)
return postNotificationToPOS(posId)
}

18. Coroutines - CódigoCoroutines - Código
runBlocking {
posList.forEach {
launch(Dispatchers.Default) {
updatePosAssortment(it.posId)
}
}
}

19. Coroutines - CódigoCoroutines - Código
val responses = mutableListOf<Response>()
runBlocking {
posList.map {
async(Dispatchers.IO) {
updatePosAssortment(it.posId).await()
}
}.forEach {
responses.add(it.await())
}
}

20. Coroutines - ProcessoCoroutines - Processo

21. Mas como funciona?Mas como funciona?

22. Continuation on Direct StyleContinuation on Direct Style
fun updatePosAssortment(posId: Int): Response{
val prices = getAmePrices()
val products = getAmeProducts()
val savePriceProductToPOS(prices, products)
return postNotificationToPOS(posId)
}

23. Continuation on Direct StyleContinuation on Direct Style
fun updatePosAssortment(posId: Int): Response{
val prices = getAmePrices()
val products = getAmeProducts()
val savePriceProductToPOS(prices, products)
return postNotificationToPOS(posId)
}
Continuation

24. Continuation on Direct StyleContinuation on Direct Style
fun updatePosAssortment(store): Response{
val prices = getAmePrices()
val products = getAmeProducts()
val savePriceProductToPOS(prices, products)
return postNotificationToPOS(posId)
}
Continuation

25. Continuation-Passing StyleContinuation-Passing Style
Continuation
fun updatePosAssortment(store): Response{
getAmePrices { prices ->
val products = getAmeProducts()
val savePriceProductToPOS(prices, products)
postNotificationToPOS(posId)
}
}

26. Continuation-Passing StyleContinuation-Passing Style
Continuation
fun updatePosAssortment(store): Response{
getAmePrices { prices ->
getAmeProducts { products ->
val savePriceProductToPOS(prices, products)
postNotificationToPOS(posId)
}
}
}

27. Continuation-Passing StyleContinuation-Passing Style
Continuation
fun updatePosAssortment(store): Response{
getAmePrices { prices ->
getAmeProducts { products ->
savePriceProductToPOS(prices, products) {
postNotificationToPOS(posId)
}
}
}
}

28. Continuation-Passing StyleContinuation-Passing Style
Continuation
fun updatePosAssortment(store): Response{
getAmePrices { prices ->
getAmeProducts { products ->
savePriceProductToPOS(prices, products) {
postNotificationToPOS(posId)
}
}
}
}

29. CPS em KotlinCPS em Kotlin
suspend fun updatePosAssortment(posId : Int): Response { ... }
Object updatePosAssortment(Int posId, Continuation<Response> cont) { ... }
Compilação JVM

30. Máquina de estadosMáquina de estados
suspend fun updatePosAssortment(posId: Int): Response{
//LABEL 0
val prices = getAmePrices()
//LABEL 1
val products = getAmeProducts()
//LABEL 2
val savePriceProductToPOS(prices, products)
//LABEL 3
return postNotificationToPOS(posId)
}

31. Máquina de estadosMáquina de estados
suspend fun updatePosAssortment(posId: Int): Response{
switch (label){
case 0:
val prices = getAmePrices()
case 1:
val products = getAmeProducts()
case 2:
val savePriceProductToPOS(prices, products)
case 3:
postNotificationToPOS(posId)
}
}

32. Máquina de estadosMáquina de estados
suspend fun updatePosAssortment(posId: Int): Response{
val sm = object : CoroutineImpl { ... }
switch (label){
case 0:
sm.label = 1
sm.posId = posId
val prices = getAmePrices(sm)
case 1:
val products = getAmeProducts()
case 2:
val savePriceProductToPOS(prices, products)
case 3:
postNotificationToPOS(posId)
}
}

33. CPU SchedulersCPU Schedulers

34. Pontos relevantesPontos relevantes
1. Coroutines com Java
2. Bibliotecas Java são usadas em Kotlin
3. “Coroutines are light-weight threads”

35. PERGUNTAS?PERGUNTAS?

36. TEMOS VAGASTEMOS VAGAS