I think this question has been already answered, b...

# compose

[Tristan Caron]

I think this question has been already answered, but I am gonna ask it again 😄

Why

val (text, setText) = +state { "Hello, World!" }

And not

var text by State("Hello, World!")

Same questions for @Composable actually

@Composable
fun MyComponent() {}

Instead of

fun MyComponent = composable { }

Maybe I should wait for an article about this?

[Fudge]

The answer to the first question is ‘why not both? ‘

[Fudge]

They both work

[Fudge]

Regarding the second question, that adds another layer of indentation (

@Composable fun x() = Text(“hello”)

becomes

fun x() = composable {
   Text(“hello”)
}

)

[Tristan Caron]

I did not know for the first one : O And regarding the second one, I am sure that the layer of indentation was the concern here. It seems to be a lot of work (to write the plugin for gradle, for intellij, etc), for such little benefit.

[Fudge]

I don’t know if they would not need to make a compiler plugin

[Fudge]

Also remember it would need to be an extension function Composer.x() = composable{}

[Fudge]

People are saying there is no need for a gradle plugin though?

[Luca Nicoletti]

You can get fun MyComponent() = composable { } to work 😧

[Luca Nicoletti]

@Fudge it’s either shipped with the version I posted on the other thread (silently, without anyone noticing) or not required

[Leland Richardson [G]]

note that var text by state { "Hello, World!" } will be the way it will work. right now the + is needed. but property delegates are indeed something i’m looking forward to being used here. they didn’t work with the new kotlin compiler backend that we rely on until recently though

[Leland Richardson [G]]

however, val text by State("Hello World") compiles, but is subtly wrong, so don’t do that

[Leland Richardson [G]]

we should probably fix by making the State constructor internal

[Fudge]

If you don’t have it as extension method you won’t have ‘can only be called in other composables’

[Leland Richardson [G]]

regarding the 2nd question

[Leland Richardson [G]]

we thought a lot about using the receiver as our method for passing around the composer

[Leland Richardson [G]]

it has a lot of similarities but is also different from what we are doing in a few ways

[Leland Richardson [G]]

i believe i went into detail about our decision making process here a while ago if you want to try and dig that up

[Leland Richardson [G]]

(it was a multi-month decision for us, so trust me, we thought long and hard about it)

[Leland Richardson [G]]

also there is some complexity here that isn’t quite “done” in terms of how @Composable works in the current compiler version

[Icaro Temponi]

What about the hook syntax? will it still be supported or the preferred way will be the var text by state { "Hello, World!" }?

[Leland Richardson [G]]

both will work. your choice

[Leland Richardson [G]]

(at least that is the current plan)

[Icaro Temponi]

awesome, thx 🙂

[Leland Richardson [G]]

all of this works because the return type of state which is State implements the componentN operators and the property delegate operators

[Tristan Caron]

@Leland Richardson [G] Thanks for your lights!

Also, I read somewhere that BLOC (mostly known in Flutter) is something that we will be able to to.

Do you think that something like this would be possible? (Quick concept)

class CounterService {
    private val counter = ConflatedBroadcastChannel(0)
    
    fun openSubscription() = counter.openSubscription()

    suspend fun increment() {
        counter.send(counter.value + 1)
    }
}

//

@Composable
fun MyComponent(counterService: CounterService) {
    Button(onclick = { counterService.increment() })
    Text(counterService.openSubscription())
}

The view would be automatically updated on new values.

[Leland Richardson [G]]

yeah, definitely.

[Leland Richardson [G]]

i have a lot of ideas around this but suspend functions don’t yet work with the kotlin IR backend so some stuff isn’t merged yet and is yet to be explored fully

[Leland Richardson [G]]

but the broad strokes are: a composable context could be thought of as a superset to a coroutine context, so you should be able to launch coroutines from inside of composable functions without any concern over what context it is launched in

[Leland Richardson [G]]

and you could use channels like your example does to invalidate recompose scopes very seamlessly

[Tristan Caron]

I am in love... Finally found the framework that do everything I want! Can’t wait to see in action, and port it to multiplatform 😛 You’re amazing guys!

[Adam Powell]

You'll probably want flows rather than channels, there are some interesting things that happen in terms of compositions that may or may not be committed, recompositions, etc. and you'll want some automatic cleanup to be at work that would be a lot easier with flows 🙂

[Tristan Caron]

But I thought flows were for “flux” that have an end, like reading a file. For me it’s similar to Sequence but async, so AsyncSequence. And channel, for something that doesn’t, like a event. I thinking like having an UserService, and if an user change some settings, like color, it is broadcast across the app.

When a component is removed from the tree, of course, we have to think of unsubscribing. But the service will be always running.

[gildor]

Flows are not only for the things that have "an end" (actually it's also true for sequences). Essentially you probably shouldn't expose any channel API, channel may be used as implementation detail, but Flow API is more safe and powerful for consumer

broadcast across the app

Right, and to subscribe on this broadcast you consume it using Flow. Under the hood it will be a channel for now, or upcoming DataFlow or Flow.share()

[Tristan Caron]

So we will be able to use flows for events?

[Tristan Caron]

How will it look like using flows?

class CounterService {
    private val counter = ConflatedBroadcastChannel(0)
    
    fun openSubscription() = counter.openSubscription()

    suspend fun increment() {
        counter.send(counter.value + 1)
    }
}

[Tristan Caron]

I found my answer here https://github.com/Kotlin/kotlinx.coroutines/blob/d66206ea6817ac178e3ed7266673ec4b9540c329/kotlinx-coroutines-core/common/src/flow/DataFlow.kt#L34

[gildor]

With DataFlow it would look like in this doc on your link, but even now, without DataFlow, you can use Flow API, just replace counter.openSubscription() with counter.asFlow()