Is it OK to group callbacks like this to be passed...

# compose

[alexhelder]

Is it OK to group callbacks like this to be passed into a composable?

data class HomeCallbacks(
    val onCallback1: () -> Unit,
    val onCallback2: () -> Unit,
    val onCallback3: () -> Unit,
)

fun HomeScreen(
    state: HomeState,
    callbacks: HomeCallbacks = HomeCallbacks()
) {
    // ...
}

[Pablichjenkov]

I have used this pattern and it is really handy, it saves typing time and your Composables signature don't bloat with so many callbacks. I actually created a mini API around it where I add interceptors to the events. Sometimes you want to intercept some specific event in a specific layer on the Composable side before it reaches the ViewModel, or the state where the callback is instantiated.

[Jonathan]

A nice solution would be to have one callback and use sealed classes to represent different events you want to observe. I think it makes the calling code cleaner and makes adding new "events" dirt simple. Using a sealed class in a when statement has to be exhaustive so you don't have to worry about forgetting to implement an event.

[Pablichjenkov]

That works great too. I actually moved to this last pattern recently. You can associate the events that are related. Likewise you can have multiple callbacks too.

[KamilH]

For sealed Event solutions, I’ve always wondered about the memory impact, especially for quickly occurring events like OnTextChanged, etc. I’ve never measured it, though, and I think this could be mitigated by using a value class
The downside is also that we are tightly coupling UI components with events unless we use lambdas everywhere and the “event sink” on the “screen” level

[Jonathan]

For text changing events, you should opt for using TextFieldState instead of a callback. Ideally most of your callbacks could be data object so you’d have as little allocations as possible.