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rbusarow
COROUTINE-FIRST
ANDROID ARCHITECTURE
Rick Busarow
Photo by Flipboard on Unsplash
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@rbusarow
Coroutines First
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12 SEPTEMBER 2018
@rbusarow
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12 SEPTEMBER 2018
@rbusarow
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http://bit.ly/Structured-Concurrency-Article
12 SEPTEMBER 2018
@rbusarow
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12 SEPTEMBER 2018
@rbusarow
http://bit.ly/Structured-Concurrency-GitHub
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@rbusarow
Structured Concurrency
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Job hierarchy
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class SomeViewModel : ViewModel() {
fun doSomething() {
val job = launch {
…
}
}
}
Pre- Structured Concurrency
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class SomeViewModel : ViewModel() {
fun doSomething() {
val job = launch {
…
}
}
}
Pre- Structured Concurrency
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class SomeViewModel : ViewModel() {
fun doSomething() {
val job = launch {
…
}
}
}
Pre- Structured Concurrency
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class SomeViewModel : ViewModel() {
fun doSomething() {
val job = launch {
…
}
}
}
Pre- Structured Concurrency
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@rbusarow
Job hierarchy
Job
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Job hierarchy
Job
Job Job
Job
Job
Job
Job
Job
Job
Job Job
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Job
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Job hierarchy
Explicit cancellation
Job
Job
Job
Job
Job
Job
Job
Job
Job Job
Job
Job
Job
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Job
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Job hierarchy
Explicit cancellation
Job
Job
Job
Job
Job
Job
Job
Job
Job Job
.cancel()
Job
Job
Job
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Job
@rbusarow
Job hierarchy
Explicit cancellation
Job
Job
Job
Job
Job
Job
Job
Job
Job
Job
Job
.cancel()
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class SomeViewModel : ViewModel() {
fun doSomething() {
val job = launch {
…
}
}
}
Pre- Structured Concurrency
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class SomeViewModel : ViewModel() {
fun doSomething() {
val job = launch {
…
}
}
}
Pre- Structured Concurrency
Completely
Autonomous
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0.26 to 1.0
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class SomeViewModel : ViewModel() {
fun doSomething() {
val job = launch {
…
}
}
}
0.26 to 1.0
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@rbusarow
class SomeViewModel : ViewModel() {
fun doSomething() {
val job = launch {
…
}
}
}
fun CoroutineScope.launch(
context: CoroutineContext = EmptyCoroutineContext,
start: CoroutineStart = CoroutineStart.DEFAULT,
block: suspend CoroutineScope.() !-> Unit
): Job { … }
0.26 to 1.0
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@rbusarow
class SomeViewModel : ViewModel(), CoroutineScope {
override val coroutineContext = Job() + Dispatchers.Main
fun doSomething() {
val job = launch {
…
}
}
}
Structured Concurrency
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class SomeViewModel : ViewModel(), CoroutineScope {
override val coroutineContext = Job() + Dispatchers.Main
fun doSomething() {
val job = launch {
…
}
}
override fun onCleared() {
super.onCleared()
coroutineContext.cancel()
}
}
Structured Concurrency
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Lifecycle
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Androidx Lifecycle
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Androidx Lifecycle
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Androidx Lifecycle
INITIALIZED
STARTED
RESUMED
CREATED
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Androidx Lifecycle
INITIALIZED
STARTED
RESUMED
CREATED
STARTED
CREATED
DESTROYED
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@rbusarow
Androidx Lifecycle
INITIALIZED
STARTED
RESUMED
CREATED
STARTED
CREATED
DESTROYED
viewModel init
viewModel.onCleared()
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Androidx Lifecycle
STARTED
RESUMED
CREATED
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Androidx Lifecycle
STARTED
RESUMED
CREATED
onCreate()
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Androidx Lifecycle
STARTED
RESUMED
CREATED
onStart()
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Androidx Lifecycle
STARTED
RESUMED
CREATED
onResume()
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Androidx Lifecycle
STARTED
RESUMED
CREATED
Lifecycle B
STARTED
RESUMED
CREATED
Lifecycle A
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@rbusarow
Androidx Lifecycle
STARTED
RESUMED
CREATED
Lifecycle C
STARTED
RESUMED
CREATED
Lifecycle B
STARTED
RESUMED
CREATED
Lifecycle A
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@rbusarow
Androidx Lifecycle
STARTED
RESUMED
CREATED
Lifecycle C
STARTED
RESUMED
CREATED
Lifecycle B
STARTED
RESUMED
CREATED
Lifecycle A
…DESTROYED? ¯\_(ツ)_/¯
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@rbusarow
class MainViewModel : ViewModel(), CoroutineScope {
override val coroutineContext: CoroutineContext = SupervisorJob() + Dispatchers.Main
val reminder = launch {
while (true) {
delay(1_000)
Log.v("MainViewModel", "still alive! --> ${UUID.randomUUID()}")
}
}
override fun onCleared() {
super.onCleared()
cancel()
}
}
ViewModel lifecycle
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class MainViewModel : ViewModel(), CoroutineScope {
override val coroutineContext: CoroutineContext = SupervisorJob() + Dispatchers.Main
val reminder = launch {
while (true) {
delay(1_000)
Log.v("MainViewModel", "still alive! --> ${UUID.randomUUID()}")
}
}
override fun onCleared() {
super.onCleared()
cancel()
}
}
ViewModel lifecycle
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class MainViewModel : ViewModel(), CoroutineScope {
override val coroutineContext: CoroutineContext = SupervisorJob() + Dispatchers.Main
val reminder = launch {
while (true) {
delay(1_000)
Log.v("MainViewModel", "still alive! --> ${UUID.randomUUID()}")
}
}
override fun onCleared() {
super.onCleared()
cancel()
}
}
ViewModel lifecycle
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@rbusarow
class MainViewModel : ViewModel(), CoroutineScope {
override val coroutineContext: CoroutineContext = SupervisorJob() + Dispatchers.Main
val reminder = launch {
while (true) {
delay(1_000)
Log.v("MainViewModel", "still alive! --> ${UUID.randomUUID()}")
}
}
override fun onCleared() {
super.onCleared()
cancel()
}
}
ViewModel lifecycle
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class MainViewModel : ViewModel() {
val reminder = viewModelScope.launch {
while (true) {
delay(1_000)
Log.v("MainViewModel", "still alive! --> ${UUID.randomUUID()}")
}
}
}
ViewModel lifecycle
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CoroutineContext
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class MainViewModel : ViewModel(), CoroutineScope {
override val coroutineContext: CoroutineContext = SupervisorJob() + Dispatchers.Main
}
CoroutineContext
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class MainViewModel : ViewModel(), CoroutineScope {
override val coroutineContext: CoroutineContext = SupervisorJob() + Dispatchers.Main
}
CoroutineContext
parent Job
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class MainViewModel : ViewModel(), CoroutineScope {
override val coroutineContext: CoroutineContext = SupervisorJob() + Dispatchers.Main
}
CoroutineContext
parent Job
default Dispatcher
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class MainViewModel : ViewModel(), CoroutineScope {
override val coroutineContext: CoroutineContext = SupervisorJob() + Dispatchers.Main
}
CoroutineContext
interface CoroutineContext {
val job: Job
val continuationInterceptor: ContinuationInterceptor
val coroutineExceptionHandler: CoroutineExceptionHandler
val coroutineName: CoroutineName
}
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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
}
CoroutineContext
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@rbusarow
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
}
CoroutineContext
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@rbusarow
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
}
CoroutineContext
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@rbusarow
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
}
CoroutineContext
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public operator fun plus(context: CoroutineContext): CoroutineContext =
if (context === EmptyCoroutineContext) this else // fast path -- avoid lambda creation
context.fold(this) { acc, element ->
val removed = acc.minusKey(element.key)
if (removed === EmptyCoroutineContext) element else {
// make sure interceptor is always last in the context (and thus is fast to get when present)
val interceptor = removed[ContinuationInterceptor]
if (interceptor == null) CombinedContext(removed, element) else {
val left = removed.minusKey(ContinuationInterceptor)
if (left === EmptyCoroutineContext) CombinedContext(element, interceptor) else
CombinedContext(CombinedContext(left, element), interceptor)
}
}
}
CoroutineContext
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@rbusarow
public operator fun plus(context: CoroutineContext): CoroutineContext =
if (context === EmptyCoroutineContext) this else // fast path -- avoid lambda creation
context.fold(this) { acc, element ->
val removed = acc.minusKey(element.key)
if (removed === EmptyCoroutineContext) element else {
// make sure interceptor is always last in the context (and thus is fast to get when present)
val interceptor = removed[ContinuationInterceptor]
if (interceptor == null) CombinedContext(removed, element) else {
val left = removed.minusKey(ContinuationInterceptor)
if (left === EmptyCoroutineContext) CombinedContext(element, interceptor) else
CombinedContext(CombinedContext(left, element), interceptor)
}
}
}
CoroutineContext
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@rbusarow
ViewModel lifecycle
http://bit.ly/Demystifying-CoroutineContext
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@rbusarow
Dispatchers
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object Dispatchers {
val Default: CoroutineDispatcher
val IO: CoroutineDispatcher
val Main: CoroutineDispatcher
val Unconfined: CoroutineDispatcher
}
Dispatchers
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object Dispatchers {
val Default: CoroutineDispatcher
val IO: CoroutineDispatcher
val Main: CoroutineDispatcher
val Unconfined: CoroutineDispatcher
}
Dispatchers
CPU-bound
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object Dispatchers {
val Default: CoroutineDispatcher
val IO: CoroutineDispatcher
val Main: CoroutineDispatcher
val Unconfined: CoroutineDispatcher
}
Dispatchers
CPU-bound
IO-bound
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object Dispatchers {
val Default: CoroutineDispatcher
val IO: CoroutineDispatcher
val Main: CoroutineDispatcher
val Unconfined: CoroutineDispatcher
}
Dispatchers
CPU-bound
IO-bound
UI
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@rbusarow
object Dispatchers {
val Default: CoroutineDispatcher
val IO: CoroutineDispatcher
val Main: CoroutineDispatcher
val Unconfined: CoroutineDispatcher
}
Dispatchers
CPU-bound
IO-bound
UI
Debugging
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object Dispatchers {
val Default: CoroutineDispatcher
val IO: CoroutineDispatcher
val Main: CoroutineDispatcher
val Unconfined: CoroutineDispatcher
}
fun doSomething() = launch(Dispatchers.IO) { … }
suspend fun doSomethingElse() = withContext(Dispatchers.Main) { … }
Dispatchers
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@rbusarow
object Dispatchers {
val Default: CoroutineDispatcher
val IO: CoroutineDispatcher
val Main: CoroutineDispatcher
val Unconfined: CoroutineDispatcher
}
fun doSomething() = launch(Dispatchers.IO) { … }
suspend fun doSomethingElse() = withContext(Dispatchers.Main) { … }
Dispatchers
Test CoroutineDispatcher?
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TestCoroutineDispatcher
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advanceTimeBy()
advanceUntilIdle()
pauseDispatcher()
resumeDispatcher()
cleanupTestCoroutines()
TestCoroutineDispatcher
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@rbusarow
class SomeViewModel : ViewModel(), CoroutineScope {
override val coroutineContext = Job() + Dispatchers.Main
fun doSomething() {
val job = launch {
…
}
}
override fun onCleared() {
super.onCleared()
coroutineContext.cancel()
}
}
CoroutineScope Injection
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@rbusarow
class SomeViewModel(val coroutineScope: CoroutineScope) : ViewModel() {
fun doSomething() {
coroutineScope.launch {
…
}
}
override fun onCleared() {
super.onCleared()
coroutineScope.cancel()
}
}
CoroutineScope Injection
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@rbusarow
val myScope = object: CoroutineScope {
override val coroutineContext = Job() + Dispatchers.Main
}
val myOtherScope = object: CoroutineScope {
override val coroutineContext = Job() + Dispatchers.Default
}
CoroutineScope Injection
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class MainCoroutineScope: CoroutineScope {
override val coroutineContext = Job() + Dispatchers.Main
}
class DefaultCoroutineScope: CoroutineScope {
override val coroutineContext = Job() + Dispatchers.Default
}
CoroutineScope Injection
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class MainCoroutineScopeImpl: MainCoroutineScope {
override val coroutineContext = Job() + Dispatchers.Main
}
class DefaultCoroutineScopeImpl: DefaultCoroutineScope {
override val coroutineContext = Job() + Dispatchers.Default
}
interface MainCoroutineScope: CoroutineScope
interface DefaultCoroutineScope: CoroutineScope
CoroutineScope Injection
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@rbusarow
class SomeViewModel(val coroutineScope: CoroutineScope) : ViewModel() {
fun doSomething() {
coroutineScope.launch {
…
}
}
override fun onCleared() {
super.onCleared()
coroutineScope.cancel()
}
}
CoroutineScope Injection
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@rbusarow
class SomeViewModel(val coroutineScope: MainCoroutineScope) : ViewModel() {
fun doSomething() {
coroutineScope.launch {
…
}
}
override fun onCleared() {
super.onCleared()
coroutineScope.cancel()
}
}
CoroutineScope Injection
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class MainCoroutineScopeImpl: MainCoroutineScope {
override val coroutineContext = Job() + Dispatchers.Main
}
interface MainCoroutineScope: CoroutineScope
class TestMainCoroutineScope: MainCoroutineScope {
override val coroutineContext = Job() + TestCoroutineDispatcher()
}
CoroutineScope Injection
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@rbusarow
fun doSomething() = launch(Dispatchers.IO) { … }
suspend fun doSomethingElse() = withContext(Dispatchers.Main) { … }
CoroutineScope Injection
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@rbusarow
No hard-coded Dispatchers
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interface DispatcherProvider {
val default: CoroutineDispatcher
val io: CoroutineDispatcher
val main: CoroutineDispatcher
val mainImmediate: CoroutineDispatcher
val unconfined: CoroutineDispatcher
}
DispatcherProvider
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@rbusarow
interface DispatcherProvider : CoroutineContext.Element {
override val key: CoroutineContext.Key<*> get() = Key
val default: CoroutineDispatcher
val io: CoroutineDispatcher
val main: CoroutineDispatcher
val mainImmediate: CoroutineDispatcher
val unconfined: CoroutineDispatcher
companion object Key : CoroutineContext.Key
}
DispatcherProvider
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class MainCoroutineScope: CoroutineScope {
override val coroutineContext = Job() + Dispatchers.Main
}
DispatcherProvider
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class MainCoroutineScopeImpl(
dispatcherProvider: DispatcherProvider = DefaultDispatcherProvider()
): MainCoroutineScope = MainCoroutineScope {
override val coroutineContext =
Job() + dispatcherProvider.main + dispatcherProvider
}
DispatcherProvider
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@rbusarow
class MainCoroutineScopeImpl(
dispatcherProvider: DispatcherProvider = DefaultDispatcherProvider()
): MainCoroutineScope = MainCoroutineScope {
override val coroutineContext =
Job() + dispatcherProvider.main + dispatcherProvider
}
DispatcherProvider
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val CoroutineContext.dispatcherProvider: DispatcherProvider
get() = get(DispatcherProvider) ?: DefaultDispatcherProvider()
DispatcherProvider
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@rbusarow
val CoroutineContext.dispatcherProvider: DispatcherProvider
get() = get(DispatcherProvider) ?: DefaultDispatcherProvider()
val CoroutineScope.mainDispatcher: CoroutineDispatcher
get() = dispatcherProvider.main
DispatcherProvider
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@rbusarow
val CoroutineContext.dispatcherProvider: DispatcherProvider
get() = get(DispatcherProvider) ?: DefaultDispatcherProvider()
val CoroutineScope.mainDispatcher: CoroutineDispatcher
get() = dispatcherProvider.main
DispatcherProvider
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@rbusarow
class SomeViewModel(val coroutineScope: MainCoroutineScope) : ViewModel() {
fun doSomething() {
coroutineScope.launch(Dispatchers.Main) {
…
}
}
override fun onCleared() {
super.onCleared()
coroutineScope.cancel()
}
}
CoroutineScope Injection
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@rbusarow
class SomeViewModel(val coroutineScope: MainCoroutineScope) : ViewModel() {
fun doSomething() {
coroutineScope.launch(coroutineScope.mainDispatcher) {
…
}
}
override fun onCleared() {
super.onCleared()
coroutineScope.cancel()
}
}
CoroutineScope Injection
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@rbusarow
class TestDispatcherProvider(
override val default: TestCoroutineDispatcher =
TestCoroutineDispatcher(),
override val io: TestCoroutineDispatcher = TestCoroutineDispatcher(),
override val main: TestCoroutineDispatcher = TestCoroutineDispatcher(),
override val mainImmediate: TestCoroutineDispatcher =
TestCoroutineDispatcher(),
override val unconfined: TestCoroutineDispatcher =
TestCoroutineDispatcher()
) : DispatcherProvider
TestDispatcherProvider
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@rbusarow
class TestDispatcherProvider(
override val default: TestCoroutineDispatcher = TestCoroutineDispatcher(),
override val io: TestCoroutineDispatcher = TestCoroutineDispatcher(),
override val main: TestCoroutineDispatcher = TestCoroutineDispatcher(),
override val mainImmediate: TestCoroutineDispatcher =
TestCoroutineDispatcher(),
override val unconfined: TestCoroutineDispatcher = TestCoroutineDispatcher()
) : DispatcherProvider
fun TestDispatcherProvider(dispatcher: TestCoroutineDispatcher):
TestDispatcherProvider =
TestDispatcherProvider(
default = dispatcher,
io = dispatcher,
main = dispatcher,
mainImmediate = dispatcher,
unconfined = dispatcher
)
TestDispatcherProvider
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@rbusarow
interface TestProvidedCoroutineScope : TestCoroutineScope,
DefaultCoroutineScope,
IOCoroutineScope,
MainCoroutineScope,
MainImmediateCoroutineScope,
UnconfinedCoroutineScope {
val dispatcherProvider: DispatcherProvider
}
TestDispatcherProvider
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class TestProvidedCoroutineScopeImpl(
override val dispatcherProvider: DispatcherProvider,
context: CoroutineContext = EmptyCoroutineContext
) : TestProvidedCoroutineScope,
TestCoroutineScope by TestCoroutineScope(context + dispatcherProvider)
TestDispatcherProvider
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@rbusarow
class TestProvidedCoroutineScopeImpl(
override val dispatcherProvider: DispatcherProvider,
context: CoroutineContext = EmptyCoroutineContext
) : TestProvidedCoroutineScope,
TestCoroutineScope by TestCoroutineScope(context + dispatcherProvider)
fun TestProvidedCoroutineScope(
dispatcher: TestCoroutineDispatcher = TestCoroutineDispatcher(),
dispatcherProvider: TestDispatcherProvider =
TestDispatcherProvider(dispatcher),
context: CoroutineContext = EmptyCoroutineContext
): TestProvidedCoroutineScope = TestProvidedCoroutineScopeImpl(
dispatcherProvider = dispatcherProvider,
context = context + dispatcher
)
TestDispatcherProvider
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@rbusarow
class TestProvidedCoroutineScopeImpl(
override val dispatcherProvider: DispatcherProvider,
context: CoroutineContext = EmptyCoroutineContext
) : TestProvidedCoroutineScope,
TestCoroutineScope by TestCoroutineScope(context + dispatcherProvider)
fun TestProvidedCoroutineScope(
dispatcher: TestCoroutineDispatcher = TestCoroutineDispatcher(),
dispatcherProvider: TestDispatcherProvider =
TestDispatcherProvider(dispatcher),
context: CoroutineContext = EmptyCoroutineContext
): TestProvidedCoroutineScope = TestProvidedCoroutineScopeImpl(
dispatcherProvider = dispatcherProvider,
context = context + dispatcher
)
val myScope = TestProvidedCoroutineScope()
TestDispatcherProvider
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@rbusarow
class SomeViewModel(val coroutineScope: MainCoroutineScope) : ViewModel() {
fun doSomething() {
coroutineScope.launch(coroutineScope.mainDispatcher) {
…
}
}
override fun onCleared() {
super.onCleared()
coroutineScope.cancel()
}
}
CoroutineScope Injection
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@rbusarow
class SomeViewModel(val coroutineScope: MainCoroutineScope) : ViewModel() {
fun doSomething() {
coroutineScope.launch(coroutineScope.mainDispatcher) {
…
}
}
override fun onCleared() {
super.onCleared()
coroutineScope.cancel()
}
}
CoroutineScope Injection
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@rbusarow
class SomeRepository {
suspend fun doSomething() = withContext(Dispatchers.IO) { ... }
}
CoroutineScope Injection
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@rbusarow
class SomeRepository {
suspend fun doSomething() = withContext(Dispatchers.IO) { ... }
}
val CoroutineContext.dispatcherProvider: DispatcherProvider
get() = get(DispatcherProvider) ?: DefaultDispatcherProvider()
CoroutineScope Injection
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@rbusarow
class SomeRepository {
suspend fun doSomething() = withContext(Dispatchers.IO) { ... }
}
val CoroutineContext.dispatcherProvider: DispatcherProvider
get() = get(DispatcherProvider) ?: DefaultDispatcherProvider()
suspend fun withIO(
context: CoroutineContext = EmptyCoroutineContext,
block: suspend CoroutineScope.() -> T
): T {
val newContext = coroutineContext.dispatcherProvider.io + context
return withContext(newContext, block)
}
CoroutineScope Injection
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@rbusarow
class SomeRepository {
suspend fun doSomething() = withIO { ... }
}
val CoroutineContext.dispatcherProvider: DispatcherProvider
get() = get(DispatcherProvider) ?: DefaultDispatcherProvider()
suspend fun withIO(
context: CoroutineContext = EmptyCoroutineContext,
block: suspend CoroutineScope.() -> T
): T {
val newContext = coroutineContext.dispatcherProvider.io + context
return withContext(newContext, block)
}
CoroutineScope Injection
Slide 99
Slide 99 text
@rbusarow
github.com/RBusarow/DispatcherProvider