How to implement AJAX in GAE GO

Question

I know it is possible to do an ajax post using jQuery Ajax but how does the call would return a value, text, html or json? Thanks!

Answer 1

There's a very good primer on creating web applications in Go here: http://golang.org/doc/articles/wiki/

The example for handling a POST is given in the saveHandler function:

func saveHandler(w http.ResponseWriter, r *http.Request) {
    title := r.URL.Path[lenPath:]
    body := r.FormValue("body")
    p := &Page{Title: title, Body: []byte(body)}
    p.save()
    http.Redirect(w, r, "/view/"+title, http.StatusFound)
}

In your case, instead of redirecting, just return a string eg.

func saveHandler(w http.ResponseWriter, r *http.Request) {
    value := r.FormValue("inputVal")
    err := saveFunction(value)
    if err == nil {
        fmt.Fprintf(w, "OK")
    } else {
       fmt.Fprintf(w, "NG")
    }
}

func main() {
    http.HandleFunc("/", indexHandler)
    http.HandleFunc("/save", saveHandler)
    http.ListenAndServe(":8080", nil)
}

.. and (since you're using jQuery), handle it with a callback as shown in http://api.jquery.com/jQuery.post/ :

$.post('/save', {inputVal: "banana"}, function(data) {
  if(data == "OK") {
    alert("Saved!");
  } else {
    alert("Save Failed!");
  }
});

If you want to return JSON, you'll need to learn how to Marshal your data, then return that like we return the string above.

Here is a link to to the JSON documentation: http://golang.org/pkg/encoding/json/#Marshal

A good way to get familiar with how to use it is to have a play around on http://play.golang.org , marshalling and unmarshalling structs and printing them out. Here's an example: http://play.golang.org/p/OHVEGzD8KW