Channel Directions {.en}

通道方向 {.zh}

::: {.en} When using channels as function parameters, you can specify if a channel is meant to only send or receive values. This specificity increases the type-safety of the program. :::

::: {.zh}

当使用通道作为函数的参数时，你可以指定这个通道是不是 只用来发送或者接收值。这个特性提升了程序的类型安全性。

:::

package main
import "fmt"

::: {.en} This ping function only accepts a channel for sending values. It would be a compile-time error to try to receive on this channel. :::

::: {.zh}

这个 ping 函数只接受发送值的通道。尝试在此通道上接收数据将会得到一个编译时错误。

:::

func ping(pings chan<- string, msg string) {
    pings <- msg
}

::: {.en} The pong function accepts one channel for receives (pings) and a second for sends (pongs). :::

::: {.zh}

pong 函数接受一个用于接收数据的通道（pings）和一个用于发送的通道（pongs）。

:::

func pong(pings <-chan string, pongs chan<- string) {
    msg := <-pings
    pongs <- msg
}
func main() {
    pings := make(chan string, 1)
    pongs := make(chan string, 1)
    ping(pings, "passed message")
    pong(pings, pongs)
    fmt.Println(<-pongs)
}

$ go run channel-directions.go
passed message