Question

I read about JSON from internet but still i have not got the grasp of it. I am reading this article

http://webcloud.se/log/AJAX-in-Django-with-jQuery/

I could not understood the first part where the function is using JSON

def xhr_test(request, format):
    if request.is_ajax():
        if format == 'xml':
            mimetype = 'application/xml'
        if format == 'json':
            mimetype = 'application/javascript'
        data = serializers.serialize(format, ExampleModel.objects.all())
        return HttpResponse(data,mimetype)
    # If you want to prevent non XHR calls
    else:
        return HttpResponse(status=400)

My Main Problems are

1. From where the function is getting format variable
2. Does format is json mean that data given to function is json or data which will be recived is json
3. Can anyone give me simple example that what will be the ouput of this function
   data = serializers.serialize(format, ExampleModel.objects.all())
4. How will I use that data when i get that response in jquery function
5. If i don’t use JSON in above function then how will the input and response back will chnage

Thanks

Answer 1

1. From where the function is getting format variable

In practice, there are lots of ways this format could be populated. HTTP provides an Accept: header that requests can use to indicate the preferred Content-Type for the response. On the client, you might use xhr.setRequestHeader('accept', 'application/json') to tell the server that you want your response in json format. In practice, though, very few frameworks actually do this. This being django, arguments to view functions are usually set in the urlconf, you might craft a urlconf like this:

urlpatterns = patterns('', 
    # ...
    (r'^xhr_test.(?<format>.*)$', 'path.to.xhr_test'),
)

2 . Does format is json mean that data given to function is json or data which will be recived is json

This particular view doesn’t do anything at all with the request body, and is certainly providing a response body in the supplied format

4 . How will I use that data when i get that response in jquery function

Depending on how complicated your request needs to be, you can use jQuery.getJSON, which will pass your callback with regular JavaScript objects that result from parsing the JSON. If you need to do a bit more work to get the request right, you can use jQuery.parseJSON to process the json data, and that will return the same JavaScript objects.