Flow'da qanday qilib oqimlarni o'tkazish mumkin? Flow…

Odatda Flow ishlash uchun boshlang'ich oqimda ishlaydi. flowOn operatori yordamida oqimni o'zgartirish mumkin.

import kotlinx.coroutines.CoroutineDispatcher // CoroutineDispatcher uchun
import kotlinx.coroutines.Dispatchers // Dispatchers uchun
import kotlinx.coroutines.flow.Flow // Flow uchun
import kotlinx.coroutines.flow.flow // flow uchun
import kotlinx.coroutines.flow.flowOn // flowOn uchun
import kotlinx.coroutines.runBlocking // runBlocking uchun

// Flow qaytaradigan funksiyaning misoli
fun simpleFlow(): Flow<Int> = flow {
    logThread("Flow boshlang'ich") // flow builder ishlayotgan threadni log qilish
    for (i in 1..3) {
        emit(i) // Qiymatlarni chiqarish
    }
}

fun main() = runBlocking {
    simpleFlow()
        .flowOn(Dispatchers.IO) // Upstream (emitterlar) Dispatchers.IO ga o'tkaziladi
        .collect { value ->
            logThread("To'plangan $value") // Qiymatlar to'planayotgan threadni log qilish
        }
}

// Threadni log qilish uchun yordamchi funksiya
fun logThread(msg: String) {
    println("[$msg] [${Thread.currentThread().name}]")
}

flowOn operatori, u bilan bog'langan operatsiyalar oldin bajariladigan threadga ta'sir qiladi (shu jumladan flow builder). flowOndan keyin keladigan operatsiyalar, flowOn argumentida ko'rsatilgan threadda bajariladi. Agar ketma-ketlikda bir nechta flowOn bo'lsa, har biri o'zidan oldingi qismga ta'sir qiladi.

Bir nechta flowOn bilan misol:

import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.flow.*
import kotlinx.coroutines.runBlocking

fun simpleFlowWithMultipleFlowOn(): Flow<String> = flow {
    logThread("Flow builder boshlang'ich") // Birinchi `flowOn`da ishlaydi
    emit("A")
    emit("B")
}.map {
    logThread("Mapping $it") // Ikkinchi `flowOn`da ishlaydi
    it.toLowerCase()
}.flowOn(Dispatchers.Default) // Ikkinchi `flowOn` map() va flow builderga ta'sir qiladi
.filter {
    logThread("Filtering $it") // `collect` chaqirilgan threadda ishlaydi (odatda main/runBlocking)
    true
}.flowOn(Dispatchers.IO) // Birinchi `flowOn` map() va flow builderga ta'sir qiladi

fun main() = runBlocking {
    simpleFlowWithMultipleFlowOn().collect { value ->
        logThread("To'plangan $value") // runBlocking (main) threadda ishlaydi
    }
}

fun logThread(msg: String) {
    println("[$msg] [${Thread.currentThread().name}]")
}

Bu misolda:

flow builder va map Dispatchers.Defaultda ishlaydi (chunki bu oxirgi flowOn ular oldidan keladi).
filter collect chaqirilgan threadda ishlaydi, ya'ni runBlocking bajariladigan threadda (odatda Main Androidda).

Muhim: flowOn oraliq bufer yaratadi va "transparant" thread o'zgarishi emas.

Flow'da qanday qilib oqimlarni o'tkazish mumkin? Flow qaysi oqimda ishlaydi?