Understanding Chan Chan's in Go

转自老外的文章：http://tleyden.github.io/blog/2013/11/23/understanding-chan-chans-in-go/

 

A channel describes a transport of sorts. You can send a thing down that transport. When using a chan chan, the thing you want to send down the transport is another transport to send things back.

They are useful when you want to get a response to something, and you don’t want to setup two channels (it’s generally considered bad practice to have data moving bidirectionally on a single 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.

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

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

Goroutine D writes a string to the response channel

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

And now we are back to where we started

Here is some code that uses chan chan’s

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package mainimport "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) {     // make a new response chan     responseChan := make(chan string)     // send the responseChan to goRoutineD     requestChan <- responseChan     // read the response     response := <-responseChan     fmt.Printf("Response: %v\n", response)}func goroutineD(requestChan chan chan string) {     // read the responseChan from the requestChan     responseChan := <-requestChan     // send a value down the responseChan     responseChan <- "wassup!"}

This code can be run on Go playground