Mar 6, 2010

Ajax form validation

Vladimir Sidorenko

There was a task to submit form with ajax, with server side validation of course. Obvious solution is to do validation and return json with erros.

I didn't like idea of writing separate view for validation and then inserting errors in form html on client side. Especially since I already had a generic template for django form with errors display.


User will see process like this:

  • User clicks 'edit' near article block
  • article is replaced with form
  • in case there are validation errors - they are shown above the form fields
  • in case there are no errors - form is replaced by article html


Server will return piece of html that will replace part of page with article or form (with errors if needed). Actually this sentence is the most important part of this blog post. Implementation is very simple and straightforward.

Well actually the fact that you can return parts of html from server is also not new idea at all. It's just only now I finally understood that using this technique you can create more complicated things than modal window or tabs


def edit_new(request, new_id):
        new = get_object_or_404()
        if request.method == 'POST':
            form = NewsForm(request.POST, instance=new)
            if form.is_valid():
                new =
                return render_to_response('include/new.html', dict(new=new))
            form = NewsForm(instance=new)
        return render_to_response('include/form.html', dict(form=form, new=new))


This html will replace article block on 'edit' button click. Javascript should be moved to separate file of course.

<script type="text/javascript">
        function submitAndLoad(input) {
                url: "{% url edit_new %}",
                data: $(input).parent().serialize(), // форма
                type: "post",
                dataType: "html",
                success: function(data) {
                    $(input).parent().parent().html(data); // article block
            return false;
        {{ form }}
        <input type="submit" value="Save" onclick="return submitAndLoad(this);"/>


<script type="text/javascript">
        function editNew(id) {
            $("#new-" + id).load("{% url edit_new %}");
            return false;

    <!-- ... -->

    <div id="new-{{ }}">
        {% include "news/new.html" %}
    <a onclick="return editNew({{ }});" href="#">Edit</a>

Code can be cleaned up of course, I just wanted to show the idea.


I'm translating this article almost five years after it was originally written and of course now it seems very childish :) Now we have angular and ajax forms are implemented a little differently. Still this old solution is not all that bad. I'd still replace one thing here - it's better to return json with html from server instead of just html.

More thoughts

Jun 27, 2018Technology
How to Work With Legacy Code: Code Refactoring Techniques

In this article we'll review general approach to working with the best kind of projects - the ones with old untested and undocumented spaghetti code and a tight schedule. We'll review anger management techniques, coping mechanisms and some refactoring tips that might come in handy.

Vladimir Sidorenko
Mar 12, 2017Technology
Creating a chat with Django Channels

Nowadays, when every second large company has developed its own instant messenger, in the era of iMessages, Slack, Hipchat, Messager, Google Allo, Zulip and others, I will tell you how to keep up with the trend and write your own chat, using django-channels 0.17.3, django 1.10.x, python 3.5.x.

Mikhail Andreev
Aug 31, 2016Technology
Angular vs React Comparison

In this article, we will compare two most popular JS Libraries (Angular vs React). Both of them were created by professionals and have been used in famous big projects.

Vladimir Sidorenko
Aug 25, 2017Technology
How to Upload Files With Django

File upload works differently from simple form inputs, which can be somewhat troublesome for beginners. Here I'll show you how to handle uploads with ease.

Pasha Volkov
Mar 6, 2010ManagementTechnology
Supplementing settings in settings_local

For local project settings, I use old trick with settings_local file:try:from settings_local import \*except ImportError:passSo in we can override variables from I didn't know how to supplement them. For example how to add line to INSTALLED_APPS without copying whole list.Yesterday I finally understood that I can import settings from settings_local:# settings_local.pyfrom settings import \*INSTALLED_APPS += (# ...)

Vladimir Sidorenko
Feb 18, 2010Technology
Absolute urls in models

Everybody knows about permalink, but it's usually used only in get_absolute_url. I prefer to use it for all related model urls.class Event(models.Model):# [email protected] edit_url(self):return ('event_edit', (, ))And then in template:<a href="{{ event.edit_url }}">Редактировать событие</a>

Vladimir Sidorenko