Jetpack Compose counter example

MainActivity.kt

package com.example.compose

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.compose.foundation.Text
import androidx.compose.foundation.clickable
import androidx.compose.foundation.layout.Column
import androidx.compose.material.Button
import androidx.compose.material.MaterialTheme
import androidx.compose.runtime.*
import androidx.compose.runtime.snapshots.snapshotFlow
import androidx.compose.ui.Modifier
import androidx.compose.ui.platform.setContent
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.flow.launchIn
import kotlinx.coroutines.flow.onEach

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            MaterialTheme() {
                Counters()
            }
        }
    }
}

class CountersModel(scope: CoroutineScope) {
    var appleCount by mutableStateOf(0)
        private set
    var orangeCount by mutableStateOf(0)
        private set
    val total by derivedStateOf { appleCount + orangeCount }

    init {
        snapshotFlow { "Total: $total" }
            .onEach(::println)
            .launchIn(scope)
    }

    fun incApples() {
        appleCount++
    }

    fun incOranges() {
        orangeCount++
    }

    fun reset() {
        appleCount = 0
        orangeCount = 0
    }
}

@Composable
fun Counters() {
    val scope = rememberCoroutineScope()
    val model = remember { CountersModel(scope) }
    Column {
        Text(
            "Apples: ${model.appleCount}",
            modifier = Modifier.clickable(onClick = model::incApples)
        )
        Text(
            "Oranges: ${model.orangeCount}",
            modifier = Modifier.clickable(onClick = model::incOranges)
        )
        Text("Total: ${model.total}")
        Button(onClick = model::reset) {
            Text("Reset")
        }
    }
}