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rbusarow COROUTINE-FIRST ANDROID ARCHITECTURE Rick Busarow Photo by Flipboard on Unsplash

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ARCHITECTURE

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ARCHITECTURE COMPONENTS

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LiveData

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class SomeViewModel(private val repository: SomeRepository) { private val _liveData = MutableLiveData() val liveData: LiveData = _liveData }

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class SomeViewModel(private val repository: SomeRepository) { private val _liveData = MutableLiveData().apply { value = repository.getTheWindsOfWinter() } val liveData: LiveData = _liveData }

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class SomeScreen : LifecycleOwner { val viewModel: SomeViewModel by lazy { … } fun onCreate() { viewModel.liveData.observe(this, Observer { str !-> tvSomeTextView.text = str }) } }

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class SomeRepository(val api: Api) { fun getTheWindsOfWinter(): String { Thread.sleep(LONG_TIME) return api.getTwow() } }

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class SomeRepository(val api: Api) { fun getTheWindsOfWinter(): LiveData { return MutableLiveData().apply { Thread.sleep(LONG_TIME) value = api.getTwow() } } }

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class SomeViewModel(private val repository: SomeRepository) { private val _liveData = MutableLiveData().apply { value = repository.getTheWindsOfWinter() } val liveData: LiveData = _liveData }

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class SomeViewModel(private val repository: SomeRepository) { val liveData: LiveData = repository.getTheWindsOfWinter() }

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class SomeRepository(val api: Api) { fun getTheWindsOfWinter(): LiveData { return MutableLiveData().apply { Thread.sleep(LONG_TIME) value = api.getTwow() } } }

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class SomeRepository(val api: Api) { fun getTheWindsOfWinter(): LiveData { return MutableLiveData().apply { api.getTwow { value = it } } } }

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class SomeRepository(val api: Api) { fun getTheWindsOfWinter(): LiveData { return MutableLiveData().apply { api.getTwow { value = it } } } }

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class SomeRepository(val api: Api) { fun getTheWindsOfWinter(): LiveData { return MutableLiveData().apply { api.getTwow { postValue(it) } } } }

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class SomeViewModel(private val repository: SomeRepository) { val liveData: LiveData = repository.getTheWindsOfWinter() }

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class SomeViewModel(private val repository: SomeRepository) { val liveData: LiveData> = Transformations.map(repository.getTheWindsOfWinter()) { novel !-> novel!!!.split("half a hundred") } }

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class SomeViewModel(private val repository: SomeRepository) { val liveData: LiveData> = Transformations.map(repository.getTheWindsOfWinter()) { novel !-> novel!!!.split("half a hundred") } }

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class SomeViewModel( private val repository: SomeRepository, private val coroutineScope: CoroutineScope ) { private val _liveData = MutableLiveData>() val liveData: LiveData> = _liveData val transform: LiveData = Transformations.map(repository.getTheWindsOfWinter()) { novel !-> coroutineScope.launch { _liveData.postValue(novel!!!.split("half a hundred”)) } } }

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class SomeViewModel( private val repository: SomeRepository, private val coroutineScope: CoroutineScope ) { private val _liveData = MutableLiveData>() val liveData: LiveData> = _liveData val transform: LiveData = Transformations.map(repository.getTheWindsOfWinter()) { novel !-> coroutineScope.launch { _liveData.postValue(novel!!!.split("half a hundred”)) } } }

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class SomeScreen : LifecycleOwner { val viewModel: SomeViewModel by lazy { … } fun onCreate() { viewModel.liveData.observe(this, Observer { str !-> tvSomeTextView.text = str }) } }

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class SomeScreen : LifecycleOwner { val viewModel: SomeViewModel by lazy { … } fun onCreate() { viewModel.transform.observe(this, Observer { }) viewModel.liveData.observe(this, Observer { str !-> tvSomeTextView.text = str }) } }

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class SomeViewModel( private val repository: SomeRepository, private val coroutineScope: CoroutineScope ) { val liveData: LiveData> = Transformations.switchMap( repository.getTheWindsOfWinter() ) { full !-> liveData(Default) { val split = full.split("half a hundred") emit(split) } } } lifecycle-livedata-ktx:2.2.0-alpha02

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class SomeViewModel( private val repository: SomeRepository, private val coroutineScope: CoroutineScope ) { val liveData: LiveData> = Transformations.switchMap( repository.getTheWindsOfWinter() ) { full !-> liveData(Default) { val split = full.split("half a hundred") emit(split) } } } lifecycle-livedata-ktx:2.2.0-alpha02

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class SomeViewModel( private val repository: SomeRepository, private val coroutineScope: CoroutineScope ) { val liveData: LiveData> = Transformations.switchMap( repository.getTheWindsOfWinter() ) { full !-> liveData(Default) { val split = full.split("half a hundred") emit(split) } } } lifecycle-livedata-ktx:2.2.0-alpha02

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class SomeViewModel( private val repository: SomeRepository, private val coroutineScope: CoroutineScope ) { val liveData: LiveData> = repository.getTheWindsOfWinter().switchMap { full !-> liveData(Default) { val split = full.split("half a hundred") emit(split) } } } lifecycle-livedata-ktx:2.2.0-alpha02

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LiveData

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LiveData ‣ Always tied to the main thread ‣ Requires LifecycleOwner ‣ Observer-heavy ‣ Written by George R. R. Martin

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Coroutines

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CoroutineScope

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interface CoroutineScope { val coroutineContext: CoroutineContext }

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CoroutineScope 
 provides
 CoroutineContext

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fun CoroutineScope.launch( context: CoroutineContext = EmptyCoroutineContext, start: CoroutineStart = CoroutineStart.DEFAULT, block: suspend CoroutineScope.() !-> Unit ): Job { val newContext = newCoroutineContext(context) val coroutine = if (start.isLazy) LazyStandaloneCoroutine(newContext, block) else StandaloneCoroutine(newContext, active = true) coroutine.start(start, coroutine, block) return coroutine }

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fun CoroutineScope.launch( context: CoroutineContext = EmptyCoroutineContext, start: CoroutineStart = CoroutineStart.DEFAULT, block: suspend CoroutineScope.() !-> Unit ): Job { val newContext = newCoroutineContext(context) val coroutine = if (start.isLazy) LazyStandaloneCoroutine(newContext, block) else StandaloneCoroutine(newContext, active = true) coroutine.start(start, coroutine, block) return coroutine }

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fun CoroutineScope.newCoroutineContext( context: CoroutineContext ): CoroutineContext { val combined = coroutineContext + context val debug = if (DEBUG) combined + CoroutineId(COROUTINE_ID.incrementAndGet()) else combined return if ( combined !!!== Dispatchers.Default !&& combined[ContinuationInterceptor] !== null ) debug + Dispatchers.Default else debug }

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fun CoroutineScope.newCoroutineContext( context: CoroutineContext ): CoroutineContext { val combined = coroutineContext + context val debug = if (DEBUG) combined + CoroutineId(COROUTINE_ID.incrementAndGet()) else combined return if ( combined !!!== Dispatchers.Default !&& combined[ContinuationInterceptor] !== null ) debug + Dispatchers.Default else debug }

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suspend builders derive CoroutineContext

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suspend fun withContext( context: CoroutineContext, block: suspend CoroutineScope.() !-> T ): T = suspendCoroutineUninterceptedOrReturn sc@ { continuation !-> val oldContext = continuation.context … }

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suspend fun withContext( context: CoroutineContext, block: suspend CoroutineScope.() !-> T ): T = suspendCoroutineUninterceptedOrReturn sc@ { continuation !-> val oldContext = continuation.context … }

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CoroutineScope is just a CoroutineContext Provider

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CoroutineScope CoroutineContext

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CoroutineScope CoroutineContext

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CoroutineScope CoroutineContext interface CoroutineContext { val job: Job val continuationInterceptor: ContinuationInterceptor val coroutineExceptionHandler: CoroutineExceptionHandler val coroutineName: CoroutineName }

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CoroutineScope CoroutineContext interface CoroutineContext { val job: Job val continuationInterceptor: ContinuationInterceptor val coroutineExceptionHandler: CoroutineExceptionHandler val coroutineName: CoroutineName }

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CoroutineScope CoroutineContext Job

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Job Structured Concurrency

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class SomeClass : CoroutineScope { val A = Job() override val coroutineContext = A fun someFunction() { val B = launch { val D = launch {} val E = launch {} } val C = launch { val F = launch {} } } }

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class SomeClass : CoroutineScope { val A = Job() override val coroutineContext = A fun someFunction() { val B = launch { val D = launch {} val E = launch {} } val C = launch { val F = launch {} } } }

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class SomeClass : CoroutineScope { val A = Job() override val coroutineContext = A fun someFunction() { val B = launch { val D = launch {} val E = launch {} } val C = launch { val F = launch {} } } }

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A

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A B

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A B C D

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A B C F E D

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class SomeClass : CoroutineScope { val A = Job() override val coroutineContext = A fun someFunction() { val B = launch { val D = launch {} val E = launch {} } val C = launch { val F = launch {} } } }

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A B C F E D

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Cancellations

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A B C F E D .cancel()

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JOB JOB JOB JOB JOB JOB JOB .cancel()

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A B C F E D .cancel()

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A B C F E D .cancel()

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Exceptions

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A B C F E D .throw(Exception(“oops”))

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A B C F E D .throw(Exception(“oops”))

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SupervisorJob

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class SomeClass : CoroutineScope { val A = Job() override val coroutineContext = A fun someFunction() { val B = launch { val D = launch {} val E = launch {} } val C = launch { val F = launch {} } } }

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class SomeClass : CoroutineScope { val A = SupervisorJob() override val coroutineContext = A fun someFunction() { val B = launch { val D = launch {} val E = launch {} } val C = launch { val F = launch {} } } }

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class SomeClass : CoroutineScope { val A = SupervisorJob() override val coroutineContext = A fun someFunction() { val B = launch { val D = launch {} val E = launch {} } val C = launch { val F = launch {} } } }

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A B C F E D SupervisorJob

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A B C F E D SupervisorJob .throw(Exception(“oops”))

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A B C F E D SupervisorJob .throw(Exception(“oops”))

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Don’t implement CoroutineScope

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class FileParser(file: File) : CoroutineScope { override val coroutineContext = Job() + Dispatchers.IO suspend fun parse(): String = TODO() }

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class FileParser(file: File) : CoroutineScope { override val coroutineContext = Job() + Dispatchers.IO suspend fun parse(): String = TODO() } class SomeOtherClass { var novel: String? = null suspend fun onUpdatedFile(file: File) { novel = FileParser(file).parse() } }

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class FileParser(file: File) : CoroutineScope { override val coroutineContext = Job() + Dispatchers.IO suspend fun parse(): String = TODO() } class SomeOtherClass { var novel: String? = null suspend fun onUpdatedFile(file: File) { FileParser(file).launch { … } } }

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class FileParser(file: File) { private val scope = CoroutineScope(Job() + Dispatchers.IO) suspend fun parse(): String = TODO() } class SomeOtherClass { var novel: String? = null suspend fun onUpdatedFile(file: File) { FileParser(file).launch { … } } }

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https://bit.ly/2y2NDuJ

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Factories

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fun SupervisorScope( continuationInterceptor: ContinuationInterceptor = Dispatchers.Default ): CoroutineScope = CoroutineScope(SupervisorJob() + continuationInterceptor)

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fun SupervisorScope( continuationInterceptor: ContinuationInterceptor = Dispatchers.Default ): CoroutineScope = CoroutineScope(SupervisorJob() + continuationInterceptor) fun DefaultCoroutineScope() = SupervisorScope(Dispatchers.Default) fun IOCoroutineScope() = SupervisorScope(Dispatchers.IO)

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Coroutine LiveData?

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LiveData !~= BroadcastChannel

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What’s a Channel?

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Channel ‣ Observable type ‣ Linked blocking queue ‣ Thread Concurrency-safe ‣ Synchronization primitive ‣ Sender and receiver have their own CoroutineScope

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suspend fun talkToYourself() { val channel = Channel() scope.launch { repeat(5) { channel.send(it) } } val output = mutableListOf() for (i in channel) { output.add(i) } output shouldBe listOf(0, 1, 2, 3, 5) }

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suspend fun talkToYourself() { val channel = Channel() scope.launch { repeat(5) { channel.send(it) } } val output = mutableListOf() for (i in channel) { output.add(i) } output shouldBe listOf(0, 1, 2, 3, 5) }

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suspend fun talkToYourself() { val channel = Channel() scope.launch { repeat(5) { channel.send(it) } } val output = mutableListOf() for (i in channel) { output.add(i) } output shouldBe listOf(0, 1, 2, 3, 5) }

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suspend fun talkToYourself() { val channel = Channel() scope.launch { repeat(5) { channel.send(it) } } val output = mutableListOf() for (i in channel) { output.add(i) } output shouldBe listOf(0, 1, 2, 3, 5) }

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suspend fun talkToYourself() { val channel = Channel() scope.launch { repeat(5) { channel.send(it) } } val output = mutableListOf() for (i in channel) { output.add(i) } output shouldBe listOf(0, 1, 2, 3, 5) } ORDER OF OPERATIONS Send 0 Receive 0 Send 1 Receive 1 …

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Buffers

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Buffers ‣ Rendezvous ‣ LinkedList ‣ Array(size) ‣ Conflated

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Emitters

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Emmitters suspend fun send(t: T) fun offer(t: T): Boolean

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BroadcastChannels

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val channel: ReceiveChannel = BroadcastChannel(CONFLATED).openSubscription()

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Broadcast buffers ‣ Array(size) ‣ Conflated ‣ No Rendezvous ‣ No LinkedList

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ReceiveChannel Vs SendChannel

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class SomeClass { private val _channel = Channel() val channel: ReceiveChannel = _channel }

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Observing!

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fun ReceiveChannel.observe( coroutineScope: CoroutineScope, observer: CoroutineScope.(t: T) !-> Unit ): Job = coroutineScope.launch { for (t in this@observe) { observer(t) } }

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fun ReceiveChannel.observe( coroutineScope: CoroutineScope, observer: CoroutineScope.(t: T) !-> Unit ): Job = coroutineScope.launch { for (t in this@observe) { observer(t) } }

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fun ReceiveChannel.observe( coroutineScope: CoroutineScope, observer: CoroutineScope.(t: T) !-> Unit ): Job = coroutineScope.launch { for (t in this@observe) { observer(t) } }

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fun ReceiveChannel.observe( coroutineScope: CoroutineScope, observer: CoroutineScope.(t: T) !-> Unit ): Job = coroutineScope.launch { for (t in this@observe) { observer(t) } }

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class SomeClass( val someRepository: SomeRepository, val scope: CoroutineScope ) { init { someRepository.channel.observe(scope) { emitted !-> println(emitted) } } }

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class SomeClass( val someRepository: SomeRepository, val scope: CoroutineScope ) { init { someRepository.channel.observe(scope) { emitted !-> println(emitted) } } }

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CoroutineScope and the Android lifecycle

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interface Screen : LifecycleOwner, CoroutineScope

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fun Screen.whileResumed(block: CoroutineScope.() !-> Job) { var job: Job? = null val observer = object : LifecycleObserver { @OnLifecycleEvent(Lifecycle.Event.ON_RESUME) fun onResume() { job = block() } @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE) fun onPause() { job!?.cancel() } } lifecycle.addObserver(observer) }

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fun Screen.whileResumed(block: CoroutineScope.() !-> Job) { var job: Job? = null val observer = object : LifecycleObserver { @OnLifecycleEvent(Lifecycle.Event.ON_RESUME) fun onResume() { job = block() } @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE) fun onPause() { job!?.cancel() } } lifecycle.addObserver(observer) }

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fun Screen.whileResumed(block: CoroutineScope.() !-> Job) { var job: Job? = null val observer = object : LifecycleObserver { @OnLifecycleEvent(Lifecycle.Event.ON_RESUME) fun onResume() { job = block() } @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE) fun onPause() { job!?.cancel() } } lifecycle.addObserver(observer) }

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fun Screen.whileResumed(block: CoroutineScope.() !-> Job) { var job: Job? = null val observer = object : LifecycleObserver { @OnLifecycleEvent(Lifecycle.Event.ON_RESUME) fun onResume() { job = block() } @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE) fun onPause() { job!?.cancel() } } lifecycle.addObserver(observer) }

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fun Screen.whileResumed(block: CoroutineScope.() !-> Job) { var job: Job? = null val observer = object : LifecycleObserver { @OnLifecycleEvent(Lifecycle.Event.ON_RESUME) fun onResume() { job = block() } @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE) fun onPause() { job!?.cancel() } } lifecycle.addObserver(observer) }

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fun Screen.whileResumed(block: CoroutineScope.() !-> Job) { var job: Job? = null val observer = object : LifecycleObserver { @OnLifecycleEvent(Lifecycle.Event.ON_RESUME) fun onResume() { job = block() } @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE) fun onPause() { job!?.cancel() } } lifecycle.addObserver(observer) }

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fun Screen.whileResumed(block: CoroutineScope.() !-> Job) { var job: Job? = null val observer = object : LifecycleObserver { @OnLifecycleEvent(Lifecycle.Event.ON_RESUME) fun onResume() { job = block() } @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE) fun onPause() { job!?.cancel() } } lifecycle.addObserver(observer) }

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Coroutining the Uncoroutine

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fun getUserProfile(): Deferred { val deferred = CompletableDeferred() api.getUserProfile() .enqueue(object : Callback { override fun onResponse(call: Call, response: Response) { deferred.complete(response.body()) } override fun onFailure(call: Call, t: Throwable) { deferred.complete(null) } }) return deferred }

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fun getUserProfile(): Deferred { val deferred = CompletableDeferred() api.getUserProfile() .enqueue(object : Callback { override fun onResponse(call: Call, response: Response) { deferred.complete(response.body()) } override fun onFailure(call: Call, t: Throwable) { deferred.complete(null) } }) return deferred }

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fun getUserProfile(): Deferred { val deferred = CompletableDeferred() api.getUserProfile() .enqueue(object : Callback { override fun onResponse(call: Call, response: Response) { deferred.complete(response.body()) } override fun onFailure(call: Call, t: Throwable) { deferred.complete(null) } }) return deferred }

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fun getUserProfile(): Deferred { val deferred = CompletableDeferred() api.getUserProfile() .enqueue(object : Callback { override fun onResponse(call: Call, response: Response) { deferred.complete(response.body()) } override fun onFailure(call: Call, t: Throwable) { deferred.complete(null) } }) return deferred }

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fun getUserProfile(): Deferred { val deferred = CompletableDeferred() api.getUserProfile() .enqueue(object : Callback { override fun onResponse(call: Call, response: Response) { deferred.complete(response.body()) } override fun onFailure(call: Call, t: Throwable) { deferred.complete(null) } }) return deferred }

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class SomeClass(val repository: ProfileRepository) { var profile: UserProfile? = null suspend fun updateProfile() { profile = repository.getUserProfile().await() } }

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class SomeClass(val repository: ProfileRepository) { var profile: UserProfile? = null suspend fun updateProfile() { profile = repository.getUserProfile().await() } }

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rbusarow rbusarow rbusarow Thanks! Rick Busarow