How to return and use an array of strings from a jQuery ajax call?

Question

I'm using Google App Engine (Python) along with jQuery for Ajax calls to the server. I have a page where I want to load up a list of strings in Javascript from an Ajax call to the server.

The server method I want to invoke:

class BrowseObjects(webapp.RequestHandler):
    def get(self):
        ids_to_return = get_ids_to_return()
        // TODO: How to return these ids to the invoking ajax call?
        self.response.out.write(ids_to_return)

The HTML page where I want to be able to access the returned ids:

    var strings_from_server = new Array();

    $.ajax({
        type: "GET",
        url: "/get_ids.html",
        success: function(responseText){
            // TODO: How to read these IDS in here?
            strings_from_server = responseText                
        },
            error: function (xhr, ajaxOptions, thrownError){
            alert(xhr.responseText);
        }
    });

My experience with Ajax is limited-- I've only used them to store data to the server (a-la POST commands) and so I really have no idea how to get data back from the server. Thanks in advance for all help

Edit: My final answer:

I've switched to a full Ajax call (to prevent from cross-domain requests) and also to handle 'error' callbacks. My working client method looks like:

         $.ajax({
            type: "GET",
            dataType: "json",
            url: "/get_ids.html",
            success: function(reponseText){
                strings_from_server = responseText                
            },
            error: function (xhr, ajaxOptions, thrownError){
                    alert(xhr.responseText);
            }
        });

Note I specify the dataType as 'json'.
And my final server function, with sahid's answer, looks like:

class BrowseObjects(webapp.RequestHandler):
    def get(self):
        ids_to_return = get_ids_to_return()
        # Note: I have to map all my objects as `str` objects
        response_json = simplejson.dumps(map(str, ids_to_return))
        self.response.out.write(response_json)

Thanks all!

Answer 1

It's probably not the cleanest solution, but it will work. Since they are just IDs, it sounds like it's safe to push them directly into a string.

class BrowseObjects(webapp.RequestHandler):
    def get(self):
       ids_to_return = get_ids_to_return()

       response_html = '["'
       response_html += ids_to_return.join('","')
       # Edit: since my ids are Key objects (not strings)
       # I had to use the following instead:
       # response_html += '","'.join(map(str, ids_to_return))
       response_html += '"]'

       self.response.out.write(response_html)

and

var strings_from_server = new Array();

$.getJSON("/get_ids.html", function(responseData){

    strings_from_server = responseData;

});

You can check to see if the response was empty incase of an error, and you can use $.each to loop through the results.

I am using jQuerys getJSON feature to automatically parse the response. Since I'm just returning a json list, it will generate the array of data in the strings_from_server variable.

Answer 2

Hello,

The SDK of Google AppEngine provided by django the lib "simplejson".

from django.utils import simplejson

So your handler maybe it simply:

from django.utils import simplejson
class BrowseObjects(webapp.RequestHandler):
    def get(self):
       ids_to_return = get_ids_to_return()
       response_json = simplejson.dumps (ids_to_return)
       self.response.out.write(response_json)

There are a good article about ajax/rpc: http://code.google.com/appengine/articles/rpc.html