What’s the idiomatic way in Kotlin to handle event...

# getting-started

[Johann Pardanaud]

What’s the idiomatic way in Kotlin to handle events in non-UI code?

In JS you declare an EventTarget, in Swift you use the delegate pattern. What could I use in Kotlin to be notified when a specific event occurs in a class instance?
In Jetpack Compose, they have a simple onClick parameter for the Button class.

My feeling here is there is no idiomatic way to handle events, am I wrong?

[Chris Fillmore]

An object that emits events could expose a Flow, which observers could collect:
https://kotlinlang.org/docs/flow.html

There is #flow for this topic fyi

[Johann Pardanaud]

What if you emit an event without any data ? 🤔

[Denys Kravchenko]

Unit typed LiveData/Flow can be used for such things

[Vladimir Vainer]

I'm using Flow for this, MutableSharedFlow to be precise. And it's working good.
And with Koin inject, it's pretty awesome.

[Johann Pardanaud]

So in my API I could create something like

interface SomeInterface {
    val onSomeEvent: Flow<Unit>
}

And subscribe to it with collect?

val someInstance: SomeInterface
someInstance.onSomeEvent.collect { println("Event received!") }

[Vladimir Vainer]

sealed class AppEvent() {
    object EventWithoutData: AppEvent()
    data class EventWithData(val name: String) : AppEvent()
}

[Vladimir Vainer]

eventFlow = MutableSharedFlow<AppEvent>()

[Johann Pardanaud]

Perfect, thank you all! 🙂