go 语言中传统的 select case 必须固定写死，即我们在编码阶段必须明确知道当前有几个 case,如下
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select{
case <- chan1:
//todo
case <- chan2:
//todo
case <- chan3:
//todo
case <- chan4:
//todo
}
如果我在编码是不确定有几个 case，只在运行是才能知道，应该如何处理? 示例代码如下
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package main
import (
"context"
"log"
"math/rand"
"reflect"
"sync"
)
const (
numChannel int = 10
)
func main() {
cases := make([]reflect.SelectCase, 0, numChannel+1)
chans := make([]chan int, 0, numChannel)
for i := 0; i < numChannel; i++ {
ch := make(chan int)
chans = append(chans, ch)
ch_case := reflect.SelectCase{
Dir: reflect.SelectRecv,
Chan: reflect.ValueOf(ch),
}
cases = append(cases, ch_case)
}
ctx, cancel := context.WithCancel(context.TODO())
cases = append(cases, reflect.SelectCase{
Dir: reflect.SelectRecv,
Chan: reflect.ValueOf(ctx.Done()),
})
var wg sync.WaitGroup
wg.Add(1)
go func() {
defer wg.Done()
for {
chosen, val, ok := reflect.Select(cases)
if !ok {
if chosen == numChannel {
log.Print("context cancel")
} else {
log.Printf("channel %d closed", chosen)
}
return
}
intVal, ok := val.Interface().(int)
if !ok {
log.Print("unexpect data type")
return
}
log.Printf("channel %d receive value %d", chosen, intVal)
}
}()
for i:=0;i<1000;i++{
idx := rand.Int()%numChannel
chans[idx] <- rand.Int()
}
cancel()
wg.Wait()
}