kotlin协程flow filter map flowOn zip combine（1）

kotlin协程flow filter map flowOn zip combine（1）

一、flow ,emit,onCompletion,collect

import kotlinx.coroutines.flow.flow
import kotlinx.coroutines.flow.onCompletion
import kotlinx.coroutines.runBlocking

fun main(args: Array) {
    runBlocking {
        flow {
            emit("fly")
        }.onCompletion {
            println("完成")
        }.collect {
            println(it)
        }
    }
}

fly
完成

二、函数作为flow

import kotlinx.coroutines.delay
import kotlinx.coroutines.flow.flow
import kotlinx.coroutines.flow.onCompletion
import kotlinx.coroutines.runBlocking

fun main(args: Array) {
    runBlocking {
        load().onCompletion {
            println("onCompletion")
        }.collect {
            println("collect $it")
        }
    }
}

fun load() = flow {
    for (i in 1..3) {
        emit(i)
        delay(100)
    }
}

collect 1
collect 2
collect 3
onCompletion

三、filter

import kotlinx.coroutines.delay
import kotlinx.coroutines.flow.filter
import kotlinx.coroutines.flow.flow
import kotlinx.coroutines.flow.onCompletion
import kotlinx.coroutines.runBlocking

fun main(args: Array) {
    runBlocking {
        load().filter {
            it > 3
        }.onCompletion {
            println("onCompletion")
        }.collect {
            println("collect $it")
        }
    }
}

fun load() = flow {
    for (i in 1..5) {
        emit(i)
        delay(100)
    }
}

collect 4
collect 5
onCompletion

四、map，重组改写数据。

import kotlinx.coroutines.delay
import kotlinx.coroutines.flow.filter
import kotlinx.coroutines.flow.flow
import kotlinx.coroutines.flow.map
import kotlinx.coroutines.flow.onCompletion
import kotlinx.coroutines.runBlocking

fun main(args: Array) {
    runBlocking {
        load().filter {
            it > 3
        }.map {
            "fly-$it"
        }.onCompletion {
            println("onCompletion")
        }.collect {
            println("collect $it")
        }
    }
}

fun load() = flow {
    for (i in 1..5) {
        emit(i)
        delay(100)
    }
}

collect fly-4
collect fly-5
onCompletion

五、flowOn

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

fun main(args: Array) {
    runBlocking {
        load().flowOn(Dispatchers.IO)
            .onCompletion {
                println("onCompletion")
            }.collect {
                println("collect $it")
            }
    }
}

fun load() = flow {
    for (i in 1..5) {
        emit(i)
        delay(100)
    }
}

collect 1
collect 2
collect 3
collect 4
collect 5
onCompletion

六、zip

import kotlinx.coroutines.delay
import kotlinx.coroutines.flow.*
import kotlinx.coroutines.runBlocking

fun main(args: Array) {
    runBlocking {
        val flow1 = flowOf(1, 2, 3).onEach {
            delay(100)
        }

        val flow2 = flowOf("a", "b", "c").onEach {
            delay(200)
        }

        flow1.zip(flow2) { i: Int, s: String ->
            "$i-$s"
        }.onCompletion {
            println("onCompletion")
        }.collect {
            println(it)
        }
    }
}

1-a
2-b
3-c
onCompletion

七、combine

import kotlinx.coroutines.delay
import kotlinx.coroutines.flow.*
import kotlinx.coroutines.runBlocking

fun main(args: Array) {
    runBlocking {
        val flow1 = flowOf(1, 2, 3).onEach {
            delay(200)
        }

        val flow2 = flowOf("a", "b", "c").onEach {
            delay(100)
        }

        flow1.combine(flow2) { i: Int, s: String ->
            "$i-$s"
        }.collect {
            println(it)
        }
    }
}

1-a
1-b
1-c
2-c
3-c

八、conflate 合并

import kotlinx.coroutines.delay
import kotlinx.coroutines.flow.*
import kotlinx.coroutines.runBlocking
import kotlin.system.measureTimeMillis

fun main(args: Array) {
    runBlocking {
        val time = measureTimeMillis {
            val f = flow {
                for (i in 1..10) {
                    delay(100)
                    emit(i)
                }
            }
            val result = f.conflate().onEach { delay(501) }
            println(result.toList())
        }

        println(time)
    }
}

[1, 5, 10]
1686

九、debounce去重

import kotlinx.coroutines.delay
import kotlinx.coroutines.flow.*
import kotlinx.coroutines.runBlocking

fun main(args: Array) {
    runBlocking {
        flow {
            emit(1)
            delay(50)

            emit(2)
            delay(40)

            emit(3)
            delay(300)

            emit(4)
            delay(30)

            emit(5)
            delay(700)
        }.debounce(300).collect{
            print(it)
        }
    }
}

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