golang select 选择器的两种方案

golang select 选择器

常规模式:

package main

import (
	"fmt"
	"strconv"
)

func main() {
	var chs1 = make(chan int)
	var chs2 = make(chan float64)
	var chs3 = make(chan string)
	var ch4close = make(chan int)
	defer close(ch4close)

	go func(c chan int, ch4close chan int) {
		for i := 0; i < 5; i++ {
			c <- i
		}
		close(c)
		ch4close <- 1
	}(chs1, ch4close)

	go func(c chan float64, ch4close chan int) {
		for i := 0; i < 5; i++ {
			c <- float64(i) + 0.1
		}
		close(c)
		ch4close <- 1
	}(chs2, ch4close)

	go func(c chan string, ch4close chan int) {
		for i := 0; i < 5; i++ {
			c <- "string:" + strconv.Itoa(i)
		}
		close(c)
		ch4close <- 1
	}(chs3, ch4close)

	done := 0
	finished := 0
	for finished < 3 {
		select {
		case v, ok := <-chs1:
			if ok {
				done = done + 1
				fmt.Println(0, v)
			}
		case v, ok := <-chs2:
			if ok {
				done = done + 1
				fmt.Println(1, v)
			}
		case v, ok := <-chs3:
			if ok {
				done = done + 1
				fmt.Println(2, v)
			}
		case _, ok := <- ch4close:
			if ok {
				finished = finished+1
			}
		}
	}
	fmt.Println("Done", done)
}

reflect设计

package main

import (
	"fmt"
	"reflect"
	"strconv"
)

func main() {
	var chs1 = make(chan int)
	var chs2 = make(chan float64)
	var chs3 = make(chan string)
	var ch4close = make(chan int)
	defer close(ch4close)

	go func(c chan int, ch4close chan int) {
		for i := 0; i < 5; i++ {
			c <- i
		}
		close(c)
		ch4close <- 1
	}(chs1, ch4close)

	go func(c chan float64, ch4close chan int) {
		for i := 0; i < 5; i++ {
			c <- float64(i) + 0.1
		}
		close(c)
		ch4close <- 1
	}(chs2, ch4close)

	go func(c chan string, ch4close chan int) {
		for i := 0; i < 5; i++ {
			c <- "string:" + strconv.Itoa(i)
		}
		close(c)
		ch4close <- 1
	}(chs3, ch4close)


	var selectCase = make([]reflect.SelectCase, 4)
	selectCase[0].Dir = reflect.SelectRecv
	selectCase[0].Chan = reflect.ValueOf(chs1)

	selectCase[1].Dir = reflect.SelectRecv
	selectCase[1].Chan = reflect.ValueOf(chs2)

	selectCase[2].Dir = reflect.SelectRecv
	selectCase[2].Chan = reflect.ValueOf(chs3)

	selectCase[3].Dir = reflect.SelectRecv
	selectCase[3].Chan = reflect.ValueOf(ch4close)

	done := 0
	finished := 0
	for finished < len(selectCase)-1 {
		chosen, recv, recvOk := reflect.Select(selectCase)

		if recvOk {
			done = done+1
			switch chosen {
			case 0:
				fmt.Println(chosen, recv.Int())
			case 1:
				fmt.Println(chosen, recv.Float())
			case 2:
				fmt.Println(chosen, recv.String())
			case 3:
				finished = finished+1
				done = done-1
				// fmt.Println("finished\t", finished)
			}
		}
	}
	fmt.Println("Done", done)

}

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