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Django generic views let the developper to quickly write common pattern to create, update, delete and show objects. There is a common problem with the create / update generic view discussed on the django developpers mail list with solutions on the django wiki. Generic view create_object generates a HttpResponse from a model name. You can then write a basic template and use the form generated by the generic view.

A basic example starting with the model.py:

class Thing(models.Model):
    name = models.CharField(maxlength=100)

views.py (note you can directly write it in your urls.py file as in the django documentation):

from myapp.models import Thing
 
def create_thing(request):
    return django.views.generic.create_update.create_object(Thing, 
             template='create.html', post_save_redirect="..")

In the urls.py file:

(r'^creatething/', "myapp.views.create_thing")

In the template create.html:

<form method="post" action="">
  <p>
    <label for="id_name">Name:</label> {{ form.name }}
  </p>
  <input type="submit" />
</form>

And, that's all ! Now, we are going to update our models:

class Element(models.Model):
    name = models.CharField(maxlength=100)
 
class Thing(models.Model):
    element = models.ForeignKey(Element)
    name = models.CharField(maxlength=100)

The default behavior of the generic_view is to generate a form with a combobox to select the foreign element from a list. The problem here, if there is a lot of Element objects, django needs to get all data from the Element table and generate an enormous combobox. We are solving this problem by using the raw_id_admin option. Note: the problem go upstream to the generic view from the AutomaticManipulator.

Supposing we are creating Thing from an element_detail page.

(r'^(?P<elementname>\w+)/creatething/$', "myapp.views.create_thing")

Add the raw_id_admin option:

class Thing(models.Model):
    element = models.ForeignKey(Element, raw_id_admin=True)
    name = models.CharField(maxlength=100)

Modify the views.py

from myapp.models import Thing, Other
 
def create_thing(request, elementname):
    element = get_object_or_404(Element, name=elementname)
    return django.views.generic.create_update.create_object(Thing, 
        template='create.html', context={'element':element}, 
        post_save_redirect="..")

Modify the template:

<form method="post" action="">
  <input type="hidden" id="id_element" name="element" value="{{element.id}}" />
  <p>
    <label for="id_name">Name:</label> {{ form.name }}
  </p>
  <input type="submit" />
</form>

Ok, the performance problem for creating a new Thing is solved, but you need to find the Element before. How ?

• generic view object_list with the paginate option
• using search criteria

Django template filters are like unix pipes. In this example, we want to create a filter that take a $Date$ Subversion keyword and modify the date and time string format. Note: that also work with CVS, because CVS and Subversion shares the same keyword syntax.

Create a templatetags directory in you application folder, touch a __init_.py and a file where you are going to write your filters, for this example svn_keyword_filters.py

You should have a directory tree looking like:

myapp/
    views.py
    templatetags/
        __init__.py
        svn_keyword_filters.py

In svn_keyword_filters.py write:

from django import template
register = template.Library()
 
@register.filter("svndate")
def svndate(value):
    return value[7:26]

In the template add something like:

<p>
  {% load svn_keyword_filters  %}
  {{ "$Date: 2006-11-02 11:45:14 +0100 (Thu, 02 Nov 2006) $"|svndate }}
</p>

Produces this html output

<p>
  2006-11-02 11:45:14
</p>

Check the Django documentation about custom template filters.

I'm using the Django framework for my project at work. Django is really great but sometimes I have difficulties to find the "good way". Today, I discovered how to do complex lookups. Starting with this models :

from django.db import models
class Recipe:
     name = models.CharField(unique=True)
class Ingredient:
     recipe = models.ForeignKey(Recipe)
     name = models.CharField()
     quantity = models.FloatField(max_digits=5, decimal_places=2)

You're looking for all recipes containing ingredient name begining by chick or named turkey ?

from myapp.models import Recipe
from django.db.models import Q
 
Recipe.objects.filter(Q(ingredient__name__startswith="chick")\
                     |Q(ingredient__name="turkey"))

Or maybe recipes with name containing "thanks giving" and using chicken as ingredient:

Recipe.objects.filter(Q(name__icontains="thanks giving")\
                     &Q(ingredient__name="chicken"))

Read more in the Django documentation.