Demystifying Coroutines

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Demystifying Coroutines Frank Tamre @tamrefrank github.com/tamzi

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2.Definition of Coroutines 3. Using Coroutines 4. Kotlin Coroutines 5. Code sample 1. Brief History of Coroutines Agenda

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Brief History of Coroutines

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ERA 1101 1950

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Ferranti Mark I 1951

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Grace Hoper and A-0 1952

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Manchester TC 1953

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Direct keyboard input to computers 1956

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Fotran introduced Math-Matic 1957

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1958

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LISP Fotran II ALGOL 58

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Melvin Conway

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Origins Brief History of coroutines

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Definition Of Coroutines

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instance of suspendable computation.

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Using Coroutines

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Non-PreEmptive multitasking

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Non-PreEmptive multitasking

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Exceptions

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Event Loops

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iterators

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Infinite Lists

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pipes

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Handle concurrency in Android

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Kotlin Coroutines

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kotlinx-coroutines library

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STEPS

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1. Import kotlinx- coroutines library

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2.Go to that function and create a suspend instance: fun suspendableLambda(block: suspend () -> Unit)

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suspend fun validateEntries(str: String): Boolean = coroutineScope { val deferred1 = async { firstValidation(str) } val deferred2 = async { secondValidation(str) } deferred1.await() && deferred2.await() }

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Coroutine builders

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Launch{} async{} runBlocking{}

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Important Activity Lifecycle

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Code sample

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1 simple DB transactional call

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fun inTransaction(f: (Connection) -> CompletableFuture ) : CompletableFuture { return this.sendQuery("BEGIN").flatMap { _ -> val p = CompletableFuture () f(this).onComplete { ty1 -> sendQuery( if (ty1.isFailure) "ROLLBACK" else "COMMIT") .onComplete { ty2 -> if (ty2.isFailure && ty1.isSuccess) p.failed((ty2 as Failure).exception) else p.complete(ty1) } } p } } With Callbacks

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suspend fun inTransaction( f: suspend (Connection) -> A): A { try { this.sendQuery("BEGIN") val result = f(this) this.sendQuery("COMMIT") return result } catch (e: Throwable) { this.sendQuery("ROLLBACK") throw e } } with coroutines