How to set initial data for Django admin model add instance form?

How can I set an initial value of a field in the automatically generated form for adding a Django model instance, before the form is displayed? I am using Django 1.3.1.

My model is the following:

class Foo(models.Model):
  title = models.CharField(max_length=50)
  description = models.TextField()

and the current admin form is really nothing special

class FooAdmin(admin.ModelAdmin):
  ordering = ('title',)

When I use the admin page to add a new instance of Foo, I get a nice form with empty fields for title and description. What I would like is that the description field is set with a template that I obtain by calling a function.

My current best attempt at getting there is this:

def get_default_content():
  return 'this is a template for a Foo description'

class FooAdminForm(django.forms.ModelForm):

  class Meta:
      model = Foo

  def __init__(self, *args, **kwargs):
      kwargs['initial'].update({'description': get_default_content()})
      super(FooAdminForm, self).__init__(self, *args, **kwargs)

class FooAdmin(admin.ModelAdmin):
  ordering = ('title',)
  form = FooAdminForm

but if I try this I get this Django error:

AttributeError at /admin/bar/foo/add/ 
   'FooForm' object has no attribute 'get'
Request Method: GET
Request URL:    http://localhost:8000/admin/bar/foo/add/
Django Version: 1.3.1
Exception Type: AttributeError
Exception Value:    'FooForm' object has no attribute 'get'
Exception Location: /www/django-site/venv/lib/python2.6/site-packages/django/forms/widgets.py in value_from_datadict, line 178

I don't know what is wrong here, and what I should do to make it work. What I also find strange about this error (apart from the fact that I see it at all) is that there is no FooForm in my code at all?

Solution

You need to include self as the first argument in your __init__ method definition, but should not include it when you call the superclass' method.

def __init__(self, *args, **kwargs):
    # We can't assume that kwargs['initial'] exists! 
    if 'initial' not in kwargs:
        kwargs['initial'] = {}
    kwargs['initial'].update({'description': get_default_content()})
    super(FooAdminForm, self).__init__(*args, **kwargs)

Having said that, a model field can take a callable for its default, so you may not have to define a custom admin form at all.

class Foo(models.Model):
    title = models.CharField(max_length=50)
    description = models.TextField(default=get_default_content)