shareIn scope

Sample.kt

import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import kotlinx.coroutines.MainScope
import kotlinx.coroutines.flow.SharedFlow
import kotlinx.coroutines.flow.SharingStarted
import kotlinx.coroutines.flow.StateFlow
import kotlinx.coroutines.flow.collect
import kotlinx.coroutines.flow.emitAll
import kotlinx.coroutines.flow.filter
import kotlinx.coroutines.flow.flow
import kotlinx.coroutines.flow.map
import kotlinx.coroutines.flow.shareIn
import kotlinx.coroutines.flow.stateIn

interface DataSource {
    fun query(args: QueryArgs): Foo

    val changedKeys: SharedFlow<Set<String>>
}

interface QueryArgs

val QueryArgs.keys: Set<String>
    get() = setOf("")

class Foo

class Repo(private val dataSource: DataSource) {

    // does this need closing? or should function-inject viewModelScope instead?
    private val scope = MainScope()

    fun queryAndWatch(args: QueryArgs): SharedFlow<Foo> {
        return flow {
            emit(dataSource.query(args))

            emitAll(
                // this is also a SharedFlow
                dataSource.changedKeys
                    .filter { changedKeys -> changedKeys.intersect(args.keys).isNotEmpty() }
                    .map { dataSource.query(args) }
            )
        }.shareIn(scope, SharingStarted.WhileSubscribed(5_000), replay = 1)
    }
}

class MyVM(repo: Repo, args: QueryArgs) : ViewModel() {

    private val data: SharedFlow<Foo> = repo.queryAndWatch(args)

    val foo: StateFlow<String> = data.map { "foo ${toString()}" }
        .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), "")
    
    val bar: StateFlow<String> = data.map { "bar ${toString()}" }
        .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), "")
}

sample_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data>
        <variable name="vm" type="MyVM" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:text="@{vm.foo}" />

        <TextView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:text="@{vm.bar}" />
        
    </LinearLayout>

</layout>