Coroutines Kotlin

Kotlin Coroutines

Master asynchronous programming in Kotlin with coroutines, flows, and structured concurrency.

Core Concepts

Basic Coroutine

fun main() = runBlocking {
    launch {
        delay(1000L)
        println("World!")
    }
    println("Hello")
}

Suspend Functions

suspend fun fetchUser(id: String): User {
    delay(1000) // Simulating network call
    return User(id, "John Doe")
}

fun main() = runBlocking {
    val user = fetchUser("123")
    println(user)
}

Async/Await

suspend fun loadData(): Data = coroutineScope {
    val user = async { fetchUser() }
    val posts = async { fetchPosts() }

    Data(user.await(), posts.await())
}

Flow

fun simpleFlow(): Flow<Int> = flow {
    for (i in 1..3) {
        delay(100)
        emit(i)
    }
}

fun main() = runBlocking {
    simpleFlow().collect { value ->
        println(value)
    }
}

Channels

fun main() = runBlocking {
    val channel = Channel<Int>()

    launch {
        for (x in 1..5) channel.send(x * x)
        channel.close()
    }

    for (y in channel) println(y)
}

Best Practices

1. Use structured concurrency
2. Handle exceptions properly
3. Use flows for streams
4. Leverage coroutine scope
5. Use dispatchers appropriately
6. Avoid GlobalScope
7. Test coroutines properly

Resources

• https://kotlinlang.org/docs/coroutines-overview.html