29-channel-directions.md

This Go code demonstrates the communication between two goroutines using channels. Let's go through it with inline comments:

package main

import "fmt"

// Function ping sends a message to the provided channel
func ping(pings chan<- string, msg string) {
    pings <- msg
}

// Function pong receives a message from one channel and sends it to another channel
func pong(pings <-chan string, pongs chan<- string) {
    msg := <-pings
    pongs <- msg
}

func main() {
    // Creating two buffered channels, 'pings' and 'pongs', each with a capacity of 1
    pings := make(chan string, 1)
    pongs := make(chan string, 1)

    // Sending a message to the 'pings' channel
    ping(pings, "passed message")

    // Executing the 'pong' function with the 'pings' and 'pongs' channels
    pong(pings, pongs)

    // Receiving and printing the final message from the 'pongs' channel
    fmt.Println(<-pongs)
}

Output

passed message

Explanation:

1. package main: Indicates that this Go file belongs to the main executable package.

2. import "fmt": Imports the "fmt" package for formatting and printing.

3. func ping(pings chan<- string, msg string) { ... }: Defines a function ping that sends a message (msg) to the provided channel (pings). The channel is specified as a send-only channel (chan<- string), meaning it can only be used for sending.

4. func pong(pings <-chan string, pongs chan<- string) { ... }: Defines a function pong that receives a message from one channel (pings) and sends it to another channel (pongs). The 'pings' channel is specified as a receive-only channel (<-chan string), and the 'pongs' channel is specified as a send-only channel (chan<- string).

5. func main() { ... }: The main function, where the execution of the program begins.

6. pings := make(chan string, 1): Creates a buffered channel named 'pings' with a capacity of 1.

7. pongs := make(chan string, 1): Creates a buffered channel named 'pongs' with a capacity of 1.

8. ping(pings, "passed message"): Calls the ping function to send the message "passed message" to the 'pings' channel.

9. pong(pings, pongs): Calls the pong function with the 'pings' and 'pongs' channels.

10. fmt.Println(<-pongs): Receives and prints the final message from the 'pongs' channel. This demonstrates the successful communication between the two goroutines.

In summary, this code illustrates how two goroutines communicate by passing a message between them using channels. The channels are used to coordinate the flow of data between concurrent parts of the program.