http.Handle（“ /”，websocket.Handler（EchoServer）EchoServer可以获取ws以外的其他参数吗？

Question

I have opened a websocket server to send data to web component,

func WebSocketServer() {
    http.Handle("/", websocket.Handler(Echoserver))
    err := http.ListenAndServe(":8081", nil)
    CheckError(err)
}

I would like to pass an additionnal argument (msg, of type String) to the handlerfunction (Echoserver).

func Echoserver(ws *websocket.Conn, msg String) {
    fmt.Println("Client Connected")
         _ := websocket.JSON.Send(ws, msg);
    }
}

Is it possible to do this with the syntax above? How do you call Echoserver with the additionnal parameter ?

Answer 1

I assume what you want here is a consistent string parameter that is returned for all connections to /. There are a couple of approaches I've used. (None of these specific code samples have been tested; I can pull some real code if they don't compile.)

One is to let the data be the receiver. I use this a most often with a struct, but any parameter will do. This only works for a single parameter (but you could of course put multiple parameters in a struct). I like this approach when the parameter is "object like." (Generally a struct that has other methods on it.)

type echoStuff string

var hey echoStuff = "Hey!"

http.Handle("/", websocket.Handler(hey.EchoServer))
err := http.ListenAndServe(":8081", nil)
CheckError(err)

func (msg echoStuff) Echoserver(ws *websocket.Conn) {
  fmt.Println("Client Connected")
   _ := websocket.JSON.Send(ws, msg);
}

Another way is with a closure. I like this approach when the parameter is "data like." (Something like a string or other simple data. Note how this approach doesn't require creating a local type.)

func WebSocketServer() {
  http.Handle("/", echoHandler("Hey!"))
  err := http.ListenAndServe(":8081", nil)
  CheckError(err)
}

func echoHandler(msg string) websocket.Handler {
  return func(ws *Conn) {
    Echoserver(ws, msg)
  }
}