Given the following viewmodel: ```class ViewModel ...

# coroutines

[Orhan Tozan]

Given the following viewmodel:

class ViewModel {
    val selectedColor: Flow<Color> = ...
    fun onNewColorSelect(newColor: Color) {
        ...
    }
}

How can the onNewColorSelect method update the selectedColor flow? With Android, you would use MutableLiveData. How would you solve this problem with Flow?

[zak.taccardi]

val selectedColorChannel = ConflatedBroadcastChannel<Color>(..)
val selectedColor: Flow<Color> = selectedColorChannel.asFlow()

[Orhan Tozan]

.

[zak.taccardi]

then selectedColorChannel.offer(color)

[zak.taccardi]

(you just need to back your Flow<T> with a ConflatedBroadcastChannel<T>, at least until StateFlow is implemented https://github.com/Kotlin/kotlinx.coroutines/issues/1082

[zak.taccardi]

remember, Channel<T> is the synchronization primitive that allows you to communicate between coroutines

[Orhan Tozan]

I read alot that Flow is encouraged over Channels, since Flow seems to use channel under the hood?

[Orhan Tozan]

And why would one use ConflatedBroadcastChannel when Flow has the .conflate() method

[zak.taccardi]

it’s just confusing because flow and channels serve two different purposes, though both seem wrappers around asynchronous emissions of T

[zak.taccardi]

Channels are a non-blocking queue of items. It’s a literal data structure

[zak.taccardi]

Passing around a Channel<T> is like passing around a List. It’s not an abstraction over observing values of T

[Orhan Tozan]

And passing around a ConflatedBroadcastChannel<T> is like passing around the latest value of T?.

[zak.taccardi]

Flows are “cold” meaning they have some abstraction around subscribing to them. If you hook up a Flow<T> to a ConflatedBroadcastChannel<T>, this abstraction allows you to register a call to .openSubscrition(), and when the Flow is closed, close the ReceiveChannel<T> you get from that .openSubscription() call

[zak.taccardi]

correct. ConflatedBroadcastChannel<T> is literally a reactive version of a regular variable like var state: T

[Orhan Tozan]

Thanks Zak, really helpful. The analogy helps alot.

[Orhan Tozan]

What would be the difference between Channel<T> and BroadcastChannel?

[Orhan Tozan]

Also, if

ConflatedBroadcastChannel<T> is literally a reactive version of a regular variable like var state: T

Does that mean people should generally use ConflatedBroadcastChannel<T> over Flow<T> with ViewModels?

[zak.taccardi]

Does that mean people should generally use ConflatedBroadcastChannel<T> over Flow<T> with ViewModels? (edited)

You actually use both

[zak.taccardi]

ViewModel_kt.kt