Go言語: channelを使ってActorっぽいことをしたい

Go言語で、Actorっぽいことができないか試してみました。Go Playgroundで動作するサンプルを試せます。

package main

import (
    "log"
    "time"
)

func main() {
    log.Println("started")
    actor := NewActor()
    go actor.React()

    // send Increment per second
    go func() {
        for i := 0; i <= 10; i++ {
            actor.Increment <- &Increment{}
            time.Sleep(1 * time.Second)
        }
    }()

    // send Decrement per two seconds
    go func() {
        for i := 0; i <= 10; i++ {
            actor.Decrement <- &Decrement{}
            time.Sleep(2 * time.Second)
        }
    }()

    // send Stop in seven seconds
    go func() {
        time.Sleep(7 * time.Second)
        actor.Stop <- &Stop{}
    }()

    // send Letter per two seconds
    go func() {
        messages := []string{"hi!", "yo!"}
        for _, msg := range messages {
            time.Sleep(2 * time.Second)
            actor.Letter <- &Letter{msg}
        }
    }()

    // wait for all messages are sent.
    time.Sleep(10 * time.Second)

    log.Println("finished")
}

type Increment struct {
}

type Decrement struct {
}

type Stop struct {
}

type Letter struct {
    Body string
}

type Actor struct {
    number    int
    Increment chan *Increment
    Decrement chan *Decrement
    Letter    chan *Letter
    Stop      chan *Stop
}

func NewActor() *Actor {
    return &Actor{
        number:    0,
        Increment: make(chan *Increment),
        Decrement: make(chan *Decrement),
        Letter:    make(chan *Letter),
        Stop:      make(chan *Stop),
    }
}

func (a *Actor) React() {
    for {
        select {
        case <-a.Increment:
            a.number += 1
            log.Printf("incremented: %d", a.number)
        case <-a.Decrement:
            a.number -= 1
            log.Printf("decremented: %d", a.number)
        case letter := <-a.Letter:
            log.Printf("letter recieved: %s", letter.Body)
        case <-a.Stop:
            log.Println("stopping")
            return
        }
    }
}

実行結果

2009/11/10 23:00:00 started
2009/11/10 23:00:00 incremented: 1
2009/11/10 23:00:00 decremented: 0
2009/11/10 23:00:01 incremented: 1
2009/11/10 23:00:02 decremented: 0
2009/11/10 23:00:02 letter recieved: hi!
2009/11/10 23:00:02 incremented: 1
2009/11/10 23:00:03 incremented: 2
2009/11/10 23:00:04 decremented: 1
2009/11/10 23:00:04 incremented: 2
2009/11/10 23:00:04 letter recieved: yo!
2009/11/10 23:00:05 incremented: 3
2009/11/10 23:00:06 decremented: 2
2009/11/10 23:00:06 incremented: 3
2009/11/10 23:00:07 stopping
2009/11/10 23:00:10 finished