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Ajax form with jQuery

Author:
Donn
Posted:
August 18, 2008
Language:
Python
Version:
.96
Tags:
ajax urls fields views jquery form errors
Score:
0 (after 0 ratings)

I recently got a form working via jQuery and Django. This was not easy for me to do and I thought I'd record my finding here.

The form submits via jQuery and the "form" plugin. Please visit jQuery's home page to find all those links.

This code handles: * urls.py -- passing both normal and 'Ajax' urls to a view.

  • views.py -- Handling both kinds of requests so that both normal and ajax submits will work.

  • The HTML template with the script for submitting and some bling.

Error handling

I like to stay DRY so the idea of checking the form for errors in javascript and checking it in Django irks me. I decided to leave that up to Django, so the form submits and gets validated on the server. The error messages are sent back to the browser and then displayed.

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Mixed code -- Sorry about that.
urls.py
===
#Direct to template: For non-ajax form.
(r'afterform/$', 'django.views.generic.simple.direct_to_template', {"template": 'contact/afterform.html',"extra_content":{"error":False} }),
	
#Handle contact form. Using a named url: Note use in template below.
#This url handles contact/ and contact/xhr : The 'xhr' is a flag to tell the
#view that this is an ajax POST. I can't recall what it stood for :)
url(r'contact/(?P<xhr>.*)$', 'scents.contact.views.contactForm',name='contactform'),

views.py
===
from django.shortcuts import render_to_response
from django.http import HttpResponseRedirect, HttpResponse
from django import forms
from django.template import RequestContext
from django.utils import simplejson

# This describes our "form" - on the server side.
class ContactForm( forms.Form ):
	subject = forms.CharField(label = "Subject",max_length=80)
	text = forms.CharField(label = "Your query",widget=forms.Textarea)
	class Media:
		# Plug in the javascript we will need:
		js = ("/media/js/jquery/jquery-1.2.6.pack.js", "/media/js/jquery/plugins/form/jquery.form.js")

# The main view:
def contactForm( request, xhr="WTF?" ): #The xhr default is being ignored. Weird.
	# Is this a POST?
	if request.method == "POST":
		form = ContactForm(request.POST)
		#Check if the <xhr> var had something passed to it.
		if xhr=="xhr":
			# Yup, this is an Ajax request.
			
			# Validate the form:
			clean = form.is_valid()

			# Make some dicts to get passed back to the browser
			rdict = {'bad':'false'}
			if not clean:
				rdict.update({'bad':'true'})
				d={}
				# This was painful, but I can't find a better way to extract the error messages:
				for e in form.errors.iteritems():
					d.update({e[0]:unicode(e[1])}) # e[0] is the id, unicode(e[1]) is the error HTML.
				# Bung all that into the dict
				rdict.update({'errs': d  })

			# Make a json whatsit to send back.
			json = simplejson.dumps(rdict, ensure_ascii=False)

			# And send it off.
			return HttpResponse( json, mimetype='application/javascript')
		# It's a normal submit - non ajax.
		else:
			if form.is_valid():
				# Move on to an okay page:
				return HttpResponseRedirect("/scents/afterform/")
	else:
		# It's not post so make a new form
		form = ContactForm()#error_class=DivErrorList)
	# Get it rollin:
	return render_to_response(
		'contact/contact.html',
		{
		"form":form,
		},
		context_instance=RequestContext(request)
		)
		

contact.html (The template)
===
{% extends "base.html" %}

{% block J%}{{form.media}}{% endblock %}

{% block CSS %}forms.css{%endblock%}


{% block JQUERY %}
// prepare the form when the DOM is ready 
$(document).ready(function() { 
	// prepare Options Object 
	var options = { 
	url: '{% url contactform "xhr"%}', // Here we pass the xhr flag
        dataType:  'json', 
	success:   processJson, //What to call after a reply from Django
	beforeSubmit: beforeForm
	};
    // bind form using ajaxForm 
    $('#tf').ajaxForm(options); //My form id is 'tf'
});

function beforeForm() { 
	$('#bt').attr("disabled","disabled"); //Disable the submit button - can't click twice
	$('.errorlist').remove(); //Get rid of any old error uls
	$('#emsg').fadeOut('slow'); //Get rid of the main error message
	return true; //Might not need this...
}

#Do stuff with server reply:
function processJson(data) { 
// This is the first time I have touched jQuery, so I'm not sure about my
// approach. It does work, but perhaps not in the best way.
	//Do we have any data at all?
	if (data) {
		// Build a var. NOTE: Make sure your id name (this is a div) is NOT THE SAME
		// as any var in javascript -- ie has a fit and barfs errors.
		e_msg = "We received your form, thank you.";
		// Did we set the 'bad' flag in Django?
		// Use eval() to turn the stuff in the data object into actual vars.
		if (eval(data.bad)) {
			e_msg = "Please check your form.";
			errors = eval(data.errs); //Again with the eval :)
			// This is very nice: Go thru the errors, build an id name and
			// then access that tag and add the HTML from the Django error
			$.each(errors,function(fieldname,errmsg)
			{
				id = "#id_" + fieldname;
				$(id).parent().before( errmsg ); //I want the error above the <p> holding the field
				});
			// re-enable the submit button, coz user has to fix stuff.
			$('#bt').attr("disabled","");
		}
		//Show the message
		$('#emsg').text( e_msg ).fadeIn("slow");
	} else {
		//DON'T PANIC :D
		$('#emsg').text("Ajax error : no data received. ").fadeIn("slow");
	}
}
{% endblock %}

{% block CONTENT %}

<div id="emsg">&nbsp;</div>

<form action="{% url contactform None %}" method="post" id="tf">
	<fieldset>
		{{ form.as_p }} 
		<input class="input" type="submit" value="Send mail" id="bt"/>
	</fieldset>
</form>

{% endblock %}

Conclusion
===
Right, that's it. I hope. If I didn't make any horrible mistakes in writing this small tut then you should be able to reproduce the effect.

HTH
\d

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Comments

PaulAik (on February 19, 2011):

When I try this on IE8, it prompts me to download the AJAX response!

Works on FF, Chrome etc - anything I could be doing wrong?

#

mischko (on February 22, 2011):

The mime type is incorrect for JSON responses. It should not be application/javascript, but application/json.

Also, the use of eval for JSON parsing is a Very Bad Thing. Use the JSON Javascript library at https://github.com/douglascrockford/JSON-js

I don't think you need the painful method of getting the error message but can probably use this (untested): if not clean: rdict.update({'bad':'true'}) rdict.update({'errs': dict(form.errors.iteritems()) })

(I don't think you need unicode for this. If you do, then use a list comprehension).

#

ermandoser (on May 25, 2011):

This snippet does not submit the form without ajax if there are no errors, correct me if I am wrong.

#

ermandoser (on June 2, 2011):

"btaylordesign" is right about xhr flag, since you can get the type of the request from HttpRequestHeader, request.is_ajax() does what you need with xhr flag. So the url regex for capturing the "xhr" parameter is also not necessary. For newbies like me, this snippet is pointing out a nice way to deal with default form errors while submitting the form via ajax. The basic idea is returning a json object to the client side then check if any errors exist. If there is not your view should create the object then return a json object with 'bad':false which states your form is submitted successfully and related objects are created on server side, so it is kind of a success message for you to evaluate on client side. You can either show errors if 'bad':true or do whatever you need to do on a successful callback if 'bad':false.

#

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