Go 语言提供了运行时反射的内置支持实现，并允许程序在反射包的帮助下操作任意类型的对象。 Golang 中的reflect.Select()函数用于执行案例列表描述的选择操作。要访问此函数，需要在程序中导入反射包。
Syntax:
Parameters: This function takes the following parameters:
- cases : This parameter is the list of cases.
Return Value: This function returns the index of the chosen case.
下面的例子说明了上述方法在 Golang 中的使用：
示例 1：
func Select(cases []SelectCase) (chosen int, recv Value, recvOK bool)
输出：
// Golang program to illustrate
// reflect.Select() Function
package main
import (
"fmt"
"reflect"
)
func main() {
c := make(chan int, 1)
vc := reflect.ValueOf(c)
succeeded := vc.TrySend(reflect.ValueOf(123))
fmt.Println(succeeded, vc.Len(), vc.Cap())
vSend, vZero := reflect.ValueOf(789), reflect.Value{}
branches := []reflect.SelectCase{
{Dir: reflect.SelectDefault, Chan: vZero, Send: vZero},
{Dir: reflect.SelectRecv, Chan: vc, Send: vZero},
{Dir: reflect.SelectSend, Chan: vc, Send: vSend},
}
// use of Select() method
selIndex, vRecv, sentBeforeClosed := reflect.Select(branches)
fmt.Println(selIndex)
fmt.Println(sentBeforeClosed)
fmt.Println(vRecv.Int())
vc.Close()
// Remove the send case branch this time,
// for it may cause panic.
selIndex, _, sentBeforeClosed = reflect.Select(branches[:2])
fmt.Println(selIndex, sentBeforeClosed)
}
示例 2：
true 1 1
1
true
123
1 false
输出：
// Golang program to illustrate
// reflect.Select() Function
package main
import (
"fmt"
"reflect"
)
func main() {
var sendCh = make(chan int)
var increaseInt = func(c chan int) {
for i := 0; i < 8; i++ {
c <- i
}
close(c)
}
go increaseInt(sendCh)
var selectCase = make([]reflect.SelectCase, 1)
selectCase[0].Dir = reflect.SelectRecv
selectCase[0].Chan = reflect.ValueOf(sendCh)
counter := 0
for counter < 1 {
// use of Select() method
chosen, recv, recvOk := reflect.Select(selectCase)
if recvOk {
fmt.Println(chosen, recv.Int(), recvOk)
} else {
counter++
}
}
}