jQuery.getJSON doesn't trigger callback

Question

Hi!
I have a html code:

<button>asd</button>
<script type = "text/javascript">
$('button').click(
    function() {
        $.getJSON('/schedule/test/', function(json) {
            alert('json: ' + json + ' ...');
        });
    }
);
</script>

and corresponding view:

def test(request):
    if request.method == 'GET':
        json = simplejson.dumps('hello world!')
        return HttpResponse(json, mimetype = 'application/json')

The view is executed (tested using print), json variable is initialised but no alert appears. What did I do wrong? I've already seen some docs on this (http://docs.jquery.com/Ajax/jQuery.getJSON#urldatacallback for example) but I didn't find an answer.

EDIT: The problem was, that HttpResponse was not imported... Unfortunately Django gave no error about it. Everything else was correct. regards
chriss

Answer 1

Are you sure the JSON is valid? take a look at the response directly or use Firebug

Answer 2

It is likely that the json is not properly formed. Sometimes this happens to me when my code, that should be producing json is generating an error. Two options:

• Use firebug to view the JSON response

• Setup error handling in your jquery code using the jQuery.ajaxSetup options such as:

    $.ajaxSetup({"error":function(XMLHttpRequest,textStatus, errorThrown) {   
        alert(textStatus);
        alert(errorThrown);
        alert(XMLHttpRequest.responseText);
    }});
  

Using the error handling for debugging is great, since you will know immediately when there is a problem with your response. You can check out the jQuery documentation for jQuery.ajax which has all of the available options for jQuery.ajaxSetup.

EDIT: A third option would be to just open the URL that should be generating the JSON and run the output through JSON Lint to validate it.

Answer 3

I ran into this a while back and rewrote a wrapper for jQuery's Ajax which allows you to pass the normal getJSON and an additional error callback per get.

http://www.nurelm.com/themanual/2010/08/09/self-indulgent-code-jquery-getjson-with-error-handling/