Back
Mar 6, 2010

Ajax form validation

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.

Task

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

Solution

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.

Implementation

views.py

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

    return render_to_response('include/form.html', dict(form=form, new=new))

form.html

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

news_list.html

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

<!-- ... -->

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

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

Update

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.

Subscribe for the news and updates

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.

Dec 1, 2016Technology
How to Use Django & PostgreSQL for Full Text Search

For any project there may be a need to use a database full-text search. We expect high speed and relevant results from this search. When we face such problem, we usually think about Solr, ElasticSearch, Sphinx, AWS CloudSearch, etc. But in this article we will talk about PostgreSQL. Starting from version 8.3, a full-text search support in PostgreSQL is available. Let's look at how it is implemented in the DBMS itself.

Nov 21, 2016Technology
Crawling FTP server with Scrapy

Welcome all who are reading this article. I was given a task of creating a parser (spider) with the Scrapy library and parsing FTP server with data. The parser had to find lists of files on the server and handle each file separately depending on the requirement to the parser.

Sep 22, 2016Technology
Angular Form Validation

In this article, we will describe some useful scripts and directives we use with angular form validation in our projects.

Mar 6, 2010TechnologyManagement
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 settings_local.py we can override variables from settings.py. 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 += (# ...)

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):# ...@models.permalinkdef edit_url(self):return ('event_edit', (self.pk, ))And then in template:<a href="{{ event.edit_url }}">Редактировать событие</a>