Observer pattern in Go language

Question

This problem is pretty common: an object should notify all its subscribers when some event occurs. In C++ we may use boost::signals or something else. But how to do this in Go language? It would be nice to see some working code example where a couple of objects are subscribed to a publisher and process notifications.

Thanks

Answer 1

This is actually pretty simple in Go. Use channels. This is the kind of thing they're made for.

type Publish struct {
    listeners []chan *Msg
}

type Subscriber struct {
    Channel chan *Msg
}

func (p *Publisher) Sub(c chan *Msg) {
    p.appendListener(c)
}

func (p *Publisher) Pub(m *Msg) {
    for _, c := range p.listeners {
        c <- Msg
    }
}

func (s *Subscriber) ListenOnChannel() {
    for {
        data := <-s.Channel
        //Process data
    }
}

func main() {
    for _, v := range subscribers {
        p.Sub(v.Channel)
        go v.ListenOnChannel()
    }
    //Some kind of wait here
}

Obviously this isn't exactly a working code sample. But it's close.

Answer 2

There is also go-observer (https://github.com/imkira/go-observer). They compare observer with channels.