Ajax form submition using Dojo for the client side JavaScript library, and SimpleJson for the client/server communication.

This will take you through all the steps required to get started and to develop a handy form submittion without reload.

What do you need

• Django
• Dojo (v0.3) ​http://dojotoolkit.org/ an open source javascript toolkit.
• Simple_Json (v1.3) ​http://svn.red-bean.com/bob/simplejson/tags/simplejson-1.3/docs/index.html used for javascript <-> python communication.

What do we want to achieve

I will use the model of my current website, a recipe one. When a registred user see the details of a recipe, the user can mark it or update their mark by selecting a small drop down list. But when the user clicks ok the whole page reloads. We will use some Ajax to make it transparent and for the fancy effect we can add fading status message like "Your mark has been updated". The select box proposes a mark from 1 to 5, it is actually a form which is sent to the server via POST, which in django link to a method in the view.py : def details(request) which do the innerwork for the details page generation.

Installing Json

get the SimpleJson from svn.

svn co http://svn.red-bean.com/bob/simplejson/trunk/ json
cd json
sudo python setup.py install

Django part

view.py

def details(request):
	[more stuff]
	if request.POST:
                # Get all the mark for this recipe
                # its not the best way i sould hava an oter entry or table, with total and nbr of marks for
                # each recipe.
		list_mark = Mark.objects.values('mark').filter(recipe__pk=r.id)
                # loop to get the total
		total = 0
		for element in list_mark:
			total+= element['mark']
                # round it
		total = round((float(total) /  len(list_mark)),1)
                # update the total
		r.total_mark= total
		# save the user mark
                r.save()

                # Now the intersting part for this tut
		import simple_json
                # it was a french string, if we dont't use unicode
                # the result at the output of json in Dojo is wrong.
		message = unicode( message, "utf-8" )
                #
		jsonList = simple_json.dumps((my_mark, total, form_message ,message))
		return HttpResponse(jsonList)
        [more stuff, if not POST return render_to_response('recettes/details.html' ...]

url.py

Just normal url.py, remember the path which will point to the wanted method.

from django.conf.urls.defaults import *

urlpatterns = patterns('',
	[...more...]
	(r'^recettes/(?P<r_cat>[-\w]+)/(?P<r_slug>[-\w]+)/$', 'cefinban.recettes.views.details'),
        [...more...]

Html template with Dojo javascript

Dojo use

{% load i18n %}
{% extends "base.html" %}
{% block script %}
 <script type="text/javascript" src="/media/js/dojo/dojo.js"></script>
 <script type="text/javascript">
 
    dojo.require("dojo.widget.Tooltip");
    dojo.require("dojo.fx.html");
    dojo.require("dojo.event.*");
    dojo.require("dojo.json");

    // point to the same url details.html	 
    function sendForm()
    {
     dojo.io.bind({
                    url: '.',
                    handler: sendFormCallback,
                    formNode: dojo.byId('myForm')
                });
    }

  function sendFormCallback(type, data, evt)
    {
    if (type == 'error')
        alert('Error when retrieving data from the server!');
    else
        // de code the simpleJson answer from django ''details'' method.
        // it populates a Js array ! straigth so cool !
    	arrayData = dojo.json.evalJson(data);
        // now we update the html using the css id as a pointer to the part 
        // we want to update
        dojo.byId("mark_total").innerHTML = arrayData[1];
        dojo.byId("mark_message").innerHTML = arrayData[2];
        dojo.byId("mark_status").innerHTML = arrayData[3];
        // and the fancy fading effect
        dojo.lfx.html.highlight("mark_status", [255, 151, 58], 700).play(300);
    }
    
    function init()
    {
        var sendFormButton = dojo.byId('sendFormButton');
        dojo.event.connect(sendFormButton, 'onclick', 'sendForm')
    }
 
    dojo.addOnLoad(init);
	
</script>

the following HTML code just comes after the upper code snipset.

[... total mark get updated, lets put css id="mark_total" ...]
{% if r.total_mark  %}<li><b>Score</b>: <span id="mark_total">{{ r.total_mark }}</span>/5</li>{% endif %}
[....]
{% if not user.is_anonymous %}
    {% ifnotequal user.id r.owner_id %}
        <form enctype="multipart/form-data" id="myForm" method="post">
            <span id="mark_message">{{mark_message}}</span>
	       <select name="select_mark">
	  	    <option value ="1" {% ifequal my_mark 1 %} selected {% endifequal %}>1</option>
	            <option value ="2" {% ifequal my_mark 2 %} selected {% endifequal %}>2</option>
	 	    <option value ="3" {% ifequal my_mark 3 %} selected {% endifequal %}>3</option>
	 	    <option value ="4" {% ifequal my_mark 4 %} selected {% endifequal %}>4</option>
	 	    <option value ="5" {% ifequal my_mark 5 %} selected {% endifequal %}>5</option>
	       </select>
       </form>
      <button id="sendFormButton">Notez</button>
      <br/>
      <span id="mark_status">{{ mark_status }}</span>
     {% endifnotequal %}
{% endif %}

And, voila.

To have a demo use guest as login, guest as password here ​http://ozserver.no-ip.com:345 or if not working here ​http://www.cefinban.net. Go to index and pick a recipe, update the mark.

You can also have a look at the screenshot here : ​http://ozserver.no-ip.com/~greg/images/ajaxdjango.png

Dreamhost and Simplejson

If you are using dreamhost for hosting please be aware that simplejson is not installed. Instead you will have to install the source of simplejson in a folder in your home directory eg /proz/json/simple_json The simple_json directory contains the required init.py for it to be loaded as a python module.

Then in your ~/.bash_profile add the directory to your python path like below.

export PYTHONPATH=$PYTHONPATH:$HOME/django/django_src:$HOME/django/django_projects:$HOME/progz/json

That will allow yout to use simpl_json in python shell. But dont forget to change django.fcgi ! Add

sys.path +=['/home/coulix/progz/json']

log out/in and try import simple_json (or simplejson depends on what source you picked)

Any troubles : coulix@…