Access variable from another function

[lennybeadle]

In my Go code, I have 2 functions:

One to parse form data (which is just the user input from a HTML form):

func formHandler(w http.ResponseWriter, r *http.Request) {
	fmt.Println("method: ", r.Method)
	r.ParseForm()
	pepperTxt := r.FormValue("name")

	fmt.Fprintf(w, pepperTxt)
}

And the other connects to a UDP socket and sends data over it:

func socketConnection() {

         hostName := "localhost"
         portNum := "6000"

         service := hostName + ":" + portNum

         RemoteAddr, err := net.ResolveUDPAddr("udp", service)

         conn, err := net.DialUDP("udp", nil, RemoteAddr)
         if err != nil {
                 log.Fatal(err)
         }

         log.Printf("Established connection to %s \n", service)
         log.Printf("Remote UDP address : %s \n", conn.RemoteAddr().String())

         defer conn.Close()

         message := []byte(**HERE IS WHERE I WANT TO PUT pepperText**)
         conn.Write(message)

}

I want to be able to access the variable “pepperTxt” in the socketConnection function. How do I do this, I’ve tried making the variable global but still no luck. Many, many thanks for any help.

[calmh (Jakob Borg)]

Ideally you would pass it as a parameter to the socketConnection() function. However, socketConnection isn’t called from formHandler, so how does it get called? How do you ensure that it’s called after formHandler (or the variable would be unset)? You can make the variable package scoped (“global”, for Go purposes), but there are things to consider like what would happen if socketConnection() is called at the same time as formHandler changes the value (this is a data race).

[gyld (Gyula Décsi)]

pepperTxt never will be available in socketConnection() as you are defining it in the formHandler function so it is not visible outside of the formHandler function

Also keep in mind that := is the shorthand notation for var something =. Both act in the same way, except := is only valid within a function or method, while the var syntax is valid everywhere.

If you want to use global variables here is a basic example: https://play.golang.org/p/6k_gtg6yh2

[lennybeadle]

Thank you, this worked! I passed it as a variable and and called ‘go socketConnection(pepperTxt)’ at the end of the formHandler and received it on the other end. Many thanks everyone!

[CurtGreen (Curtis Allyn Green)]

I’d suggest, and this is assuming that you are going to call your socketConnection() function from within your handler to write your pepperText as a message to the connection, that you pass your pepperText variable into your socketConnection function, and use it that way.

func formHandler(w http.ResponseWriter, r *http.Request) {
	fmt.Println("method: ", r.Method)
	r.ParseForm()
	pepperTxt := r.FormValue("name")
     
        socketConnection(pepperText)
	fmt.Fprintf(w, pepperTxt)
}

You’ll have to update your socketConnection function, which might warrant a name change to something like socketConnectionMessage, but code wise you’d need to do this:

func socketConnection(pepperText string) {

         hostName := "localhost"
         portNum := "6000"

         service := hostName + ":" + portNum

         RemoteAddr, err := net.ResolveUDPAddr("udp", service)

         conn, err := net.DialUDP("udp", nil, RemoteAddr)
         if err != nil {
                 log.Fatal(err)
         }

         log.Printf("Established connection to %s \n", service)
         log.Printf("Remote UDP address : %s \n", conn.RemoteAddr().String())

         defer conn.Close()

         message := []byte(pepperText)
         conn.Write(message)

}