Kt. Academy

Part 1: Understanding Kotlin Coroutines

Why Kotlin Coroutines?

Sequence builder

Exercise: Factorial sequence

Exercise: Prime numbers sequence

How does suspension work?

Exercise: Callback function wrappers

Exercise: Continuation storage

Coroutines under the hood

Exercise: What is stored by a continuation?

Coroutines: built-in support vs library

Part 2: Kotlin Coroutines library

Starting coroutines

Exercise: UserDetailsRepository

Exercise: BestStudentUseCase

Exercise: CommentService

Exercise: mapAsync

The bigger picture

Coroutine context

Exercise: Understanding context propagation

Exercise: CounterContext

Dispatchers

Exercise: Using dispatchers

Exercise: DiscNewsRepository

Exercise: Experiments with dispatchers

Job and coroutine lifecycle

Cancellation

Exercise: Correct mistakes with cancellation

Exception handling

Constructing a coroutine scope

Exercise: NotificationSender

Exercise: BaseViewModel

Synchronizing access to mutable state

Exercise: UserDownloader

Exercise: CompanyDetailsRepository

Exercise: CancellingRefresher

Exercise: TokenRepository

Exercise: Suspended lazy

Exercise: mapAsync with concurrency limit

Testing Kotlin Coroutines

Exercise: Test UserDetailsRepository

Exercise: Testing mapAsync

Exercise: Testing the NotificationSender class

Exercise: Testing a View Model

Part 3: Channel and Flow

Channel

Exercise: UserRefresher

Exercise: Cafeteria simulation

Select

Exercise: raceOf

Actors

Hot and cold data sources

Exercise: All users flow

Exercise: distinct

Flow lifecycle functions

Exercise: TemperatureService

Exercise: NewsViewModel

Flow processing

merge, zip and combine

fold and scan

flatMapConcat, flatMapMerge and flatMapLatest

Distinct until changed

buffer and conflate

Terminal operations

Exercise: ProductService

Exercise: Flow Kata

Exercise: MessageService

SharedFlow and StateFlow

Exercise: Update ProductService

Exercise: Update TemperatureService

Exercise: LocationService

Exercise: PriceService

Exercise: NewsViewModel using stateIn

Testing flow

Exercise: Flow testing

Part 4: Kotlin Coroutines in practice

Common use cases

Data/Adapters Layer

Domain Layer

Presentation/API/UI layer

Summary

Kotlin Coroutines library was designed to suit our typical backend and Android use cases. That means, that even though every problem can be solved in many ways, for most situations, there are well established patterns that should be preferred. Some of them are expressed by Kotlin Coroutines creators themselves, while others are established by discussions in our community. I collected those use cases, and I would like to present my vision of how Kotlin Coroutines should be used in typical use cases, in typical applications.

Using coroutines from other languages

Launching coroutines vs. suspending functions

Best practices