Advanced Coroutine Concepts @mambo_bryan 01

02 Design Centric Engineer Brian Odhiambo Dishwasher @ Baobab Circle Co-organizer @ KotlinKenya Maintaining @ KotlinBits Yeah am all about that UI/UX & Kotlin

Concurrency but... Structured 03 jobs! jobs! jobs! Jobs What are Jobs and what is their lifecycle... Builders How can you use builders to create coroutines Contexts What are contexts and what is context switching

The Builders What are builders and how can you use them

suited when no result is needed Scope.launch { ... } suited when a result is needed Scope.async { ... } What are coroutine builders? serve as extensions to CoroutineScope gives you more control over lifecycle and behaviour of a coroutine return a Job Functions which are used to launch coroutines

An Example Builders launch & async import kotlinx.coroutines.* suspend fun main() { val job = GlobalScope.launch { println("Searching for a Book") } val job2 = GlobalScope.async { println("Currently in the Library") delay(1000) "Found : Kotlin In Action Edition 2" } println(job) println(job2) println("-".repeat(20)) println(job2.await()) Thread.sleep(2000) } "coroutine#1":StandaloneCoroutine{Active}@5479e3f "coroutine#2":DeferredCoroutine{Active}@42f30e0a -------------------- Currently in the Library Searching for a Book Found : Kotlin In Action Edition 2 06

The Context What are contexts and what is context switching

dictates how the coroutines related to threads dispatcher represent the cancellable task needed to run job What's a coroutine context? represented CoroutineContext interface contain a Job and Dispatcher used to execute the coroutine Immutable key-value pair that contains various data available to the coroutine

An Example Coroutine context in purple import kotlinx.coroutines.* fun CoroutineScope.working(){ println("I'm working in thread ${Thread.currentThread().name}") } fun main() = runBlocking { launch { working() } launch(Dispatchers.Unconfined) { working() } launch(Dispatchers.Default) { working() } launch(CoroutineName("MyOwnThread")) { working() } } I'm working in thread main @coroutine#3 I'm working in thread DefaultDispatcher-worker-1 @coroutine#4 I'm working in thread main @coroutine#2 I'm working in thread main @MyOwnThread#5 06

What is context switching? running a coroutine in a different thread Changing the context in which a coroutine runs Example import kotlinx.coroutines.* suspend fun main(){ doNetworkStuff() } suspend fun updateUi(){ withContext(Dispatchers.Main){ ... } } suspend fun doNetworkStuff(){ withContext(Dispatchers.IO){ ... updateUi() } }

The Jobs What are Jobs and what is their lifecycle

new created but not started start() / join() What are jobs? track task states and cancel check if isActive, isCancelled, isCompleted The lifecycle of the concurrent task active started but not completed completing waiting for children to complete completed finished and completed children

An Example Lifecycle check & update import kotlinx.coroutines.* suspend fun main() { val job = GlobalScope.launch { var i = 1 while(isActive){ println("Value : ${i++}") } } delay(20) job.cancel() } -------------------------------------- Value : 1 Value : 2 Value : 3 Value : 4 Value : 5 ... 06

Next Session Advanced Coroutine Concepts

Dispatchers Android specific dispatchers and where they are used In-Depth Guide to Android Coroutines 14 Scopes Different android specific scopes and where to use each and so much more!

One Last Thing For the community

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16 mambo_bryan MamboBryan Thank you! Have a nice Kotlin KotlinBits kotlinbits.vercel.app