通道的基本傳送和接收都阻塞。但是,可以使用select
和default
子句來實現非阻塞傳送,接收,甚至非阻塞多路選擇(select
)。
這裡是一個非阻塞接收。如果訊息上有可用的值,則選擇將使用該值的<-message
大小寫。如果不是,它會立即採用預設情況。
非阻塞傳送工作類似。
可以使用多個上面的預設子句來實現多路非阻塞選擇(select
)。這裡嘗試對訊息(message
)和信號(signals
)的非阻塞接收。
所有的範例程式碼,都放在
F:\worksp\golang
目錄下。安裝Go程式設計環境請參考:/2/23/798.html
non-blocking-channel-operations.go
的完整程式碼如下所示 -
package main
import "fmt"
func main() {
messages := make(chan string)
signals := make(chan bool)
// Here's a non-blocking receive. If a value is
// available on `messages` then `select` will take
// the `<-messages` `case` with that value. If not
// it will immediately take the `default` case.
select {
case msg := <-messages:
fmt.Println("received message", msg)
default:
fmt.Println("no message received")
}
// A non-blocking send works similarly.
msg := "hi"
select {
case messages <- msg:
fmt.Println("sent message", msg)
default:
fmt.Println("no message sent")
}
// We can use multiple `case`s above the `default`
// clause to implement a multi-way non-blocking
// select. Here we attempt non-blocking receives
// on both `messages` and `signals`.
select {
case msg := <-messages:
fmt.Println("received message", msg)
case sig := <-signals:
fmt.Println("received signal", sig)
default:
fmt.Println("no activity")
}
}
執行上面程式碼,將得到以下輸出結果 -
F:\worksp\golang>go run non-blocking-channel-operations.go
no message received
no message sent
no activity