golang go语言通道类型的通道示例 通道的通道

时间:2022-03-27 03:05:16

几点注意:go的无缓存通道

通道make 创建后,即使里面是空的,也可以取里面内容。但是程序会被阻塞。

通道的规则是没人取,是不能往里面放的。放的线程会阻塞。

最外层的requestChan相当于一个总线或媒介。

生产者goroutineD直接从requestChan通道里面再取一个内部通道responseChan,这时不管responseChan创建没有,如果没有的话会阻塞,直到取到后,往responseChan通道里面扔内容。

消费者goroutineC创建一个内部通道responseChan,然后就可以提取里面的内容。如果没有阻塞直到收到。

收取开始后,requestChan中介通道里面就没有responseChan内部通道了?

package main

import "fmt"
import "time" func main() { // make the request chan chan that both go-routines will be given
requestChan := make(chan chan string) // start the goroutines
go goroutineC(requestChan)
go goroutineD(requestChan) // sleep for a second to let the goroutines complete
time.Sleep( * time.Second) } func goroutineC(requestChan chan chan string) {
time.Sleep( * time.Second) fmt.Println("goroutineC create response chan.")
// make a new response chan
responseChan := make(chan string) // send the responseChan to goRoutineD
requestChan <- responseChan fmt.Println("goroutineC waiting to read.")
// read the response
response := <-responseChan fmt.Println("goroutineC get Response: ", response) } func goroutineD(requestChan chan chan string) { // read the responseChan from the requestChan
fmt.Println("\t\tgoroutineD wait to get response chan.")
responseChan := <-requestChan
fmt.Println("\t\tgoroutineD has gotten response chan.")
fmt.Println("\t\tgoroutineD sleep 5 minutes.")
time.Sleep( * time.Second)
// send a value down the responseChan
fmt.Println("\t\tgoroutineD send wassup.")
responseChan <- "wassup!" }

改成如下代码执行,发现通道的内容生成好之后也无法放入通道,需要有人取内容时,才能放入。这是go的无缓存通道规则

package main

import "fmt"
import "time" func main() { // make the request chan chan that both go-routines will be given
requestChan := make(chan chan string) // start the goroutines
go goroutineC(requestChan)
go goroutineD(requestChan) // go goroutineC(requestChan)
// go goroutineD(requestChan) // sleep for a second to let the goroutines complete
time.Sleep( * time.Second) } func goroutineC(requestChan chan chan string) { fmt.Println("goroutineC create response chan.")
// make a new response chan responseChan := make(chan string) // send the responseChan to goRoutineD
requestChan <- responseChan fmt.Println("goroutineC waiting to read.")
// read the response
response := <-responseChan fmt.Println("goroutineC get Response: ", response) ////read again/////////
// read the response
response = <-responseChan fmt.Println("goroutineC get Response: ", response) } func goroutineD(requestChan chan chan string) {
time.Sleep( * time.Second)
// read the responseChan from the requestChan
fmt.Println("\t\tgoroutineD wait to get response chan.")
responseChan := <-requestChan
fmt.Println("\t\tgoroutineD has gotten response chan.")
fmt.Println("\t\tgoroutineD sleep 5 minutes.")
time.Sleep( * time.Second)
// send a value down the responseChan
fmt.Println("\t\tgoroutineD send wassup.")
responseChan <- "wassup!" /////Send again to check if response chan dissapear///////////////
fmt.Println("\t\tgoroutineD sleep 5 minutes.")
time.Sleep( * time.Second)
// send a value down the responseChan
fmt.Println("\t\tgoroutineD send w22222222222.")
responseChan <- "w22222222222!" }
执行结果:
goroutineC create response chan.
goroutineD wait to get response chan.
goroutineD has gotten response chan.
goroutineD sleep 5 minutes.
goroutineC waiting to read.
goroutineD send wassup.
goroutineD sleep 5 minutes.
goroutineC get Response: wassup!
goroutineD send wassup.
goroutineC get Response: w22222222222!

参考:http://tleyden.github.io/blog/2013/11/23/understanding-chan-chans-in-go/

https://www.goin5minutes.com/blog/channel_over_channel/

Visual time lapse walkthrough

Keep in mind that Goroutine C is the “real consumer” even though it will be the one which writes to the request channel.

The request channel starts out empty.

golang go语言通道类型的通道示例 通道的通道

Goroutine C passes a “response channel” to go routine D via the request channel

golang go语言通道类型的通道示例 通道的通道

Goroutine C starts reading from the (still empty) response channel.

golang go语言通道类型的通道示例 通道的通道

Goroutine D writes a string to the response channel

golang go语言通道类型的通道示例 通道的通道

Goroutine C now is able to read a value from response channel, and get’s the “wassup!” message

golang go语言通道类型的通道示例 通道的通道

And now we are back to where we started

golang go语言通道类型的通道示例 通道的通道