Pass method on struct as callback in golang

Question

Is it possible to pass a method on a struct as a callback function in golang ?

E.g. Register a message handler :

func (mc MQTTClient) MessageHandler(client MQTT.Client, msg MQTT.Message) {
   fmt.Printf("TOPIC: %s\n", msg.Topic())
   fmt.Printf("MSG: %s\n", msg.Payload())
}

func (mc MQTTClient) AddMessageHandler(){
  //..
  //subscribe to the topic /go-mqtt/sample and request messages to be delivered
  //at a maximum qos of zero, wait for the receipt to confirm the subscription

  if token := c.Subscribe("go-mqtt/sample", 0, mc.MessageHandler); token.Wait() && token.Error() != nil {
                    fmt.Println(token.Error())
                    os.Exit(1)
  }
}

Thank you very much !

Did you try it? Did it work? If not: What did the compiler tell you? — Volker
– Volker, Commented Nov 29, 2016 at 13:44
Problem solved. The program terminated with a runtime error because of a nil pointer dereference. Therefore I have concluded that the passing of the function is wrong but the error was an assignment in a non-pointer method receiver before that. Sorry for your waste of time. :forgiveme: — aljoshare
– aljoshare, Commented Nov 29, 2016 at 15:04

Franck Jeannin · Accepted Answer · 2016-12-01 13:14:13Z

3

Golang has first class functions, you can pass them as parameters https://golang.org/doc/codewalk/functions/ You may also want to look at this https://dave.cheney.net/2016/11/13/do-not-fear-first-class-functions

edited Dec 1, 2016 at 13:14

answered Nov 29, 2016 at 13:33

Franck Jeannin

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Comments

Ken Bloom · Accepted Answer · 2016-11-29 13:44:59Z

1

What you've written appears to be correct.

answered Nov 29, 2016 at 13:44

Ken Bloom

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