Golang Working with types

Question

The Problem

I need some help working with types in Golang, I get super confused. I am trying to alter the websocket chat example from Gorilla, and I want to pass in JSON and process it accordingly. I need to be able to set for example a user, and send a message to the websocket.

In the current implementation all it does is receive a string, and relays it back by broadcasting it to all connected clients.

For example I want to be able to set a data structure as follows and process it differently.

Incoming user would be:

{
  'type': "user",
  'value': "John Doe"
}

Incomming message would be:

{
  'type': "message",
  'value': "Hi There, how are you?"
}

Please refer to the following code: https://github.com/gorilla/websocket/blob/master/examples/chat/conn.go#L52

for {
    _, message, err := c.ws.ReadMessage()
    if err != nil {
        break
    }
    h.broadcast <- message
}

Data

So the above code works for single strings, because all the server does is pass the incoming message from any client to all. But I want to be able to save users, and send the list of active users back to the client along with the new message.

To do this, in my mind I will need to handle the different incoming messages differently. I tried to unmarchal the incomming message, but when I print out the type it's this:

2015/11/24 20:03:10 []uint8

THE QUESTION

How do I go about reading this input stream, and unmarshal it to JSON? This is the debugging I added to the section:

for {
    _, dataString, err := c.ws.ReadMessage()
    if err != nil {
        break
    }

    log.Println(reflect.TypeOf(dataString))

    var data MessageData
    err = json.Unmarshal(dataString, &data)
    log.Println(data.Type)
    log.Println(data.Value)

    if err != nil {
        log.Println(err)
    }

    h.broadcast <- dataString
}

Which Returns

2015/11/24 20:03:10 []uint8
2015/11/24 20:03:10 
2015/11/24 20:03:10

Rudi Strydom · Accepted Answer · 2015-11-24 18:41:49Z

3

Sorry, I was being a bit stupid with this. The message is already a byte type interface. I didn't properly encode the data on the HTML / JavaScript frontend before sending it to the backend.

What worked was stringifying it in the frontend:

var data = {};
data.type = "user";
data.value = user.val();
conn.send(JSON.stringify(data));
JSON.stringify(data)

Then I was able to unmarshall the JSON:

2015/11/24 20:36:04 {user fhgfhg}
2015/11/24 20:36:04 user
2015/11/24 20:36:04 fhgfhg

answered Nov 24, 2015 at 18:41

Rudi Strydom

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