How do you modify the default widget for all builtin form fields of a certain type in Django?

Question

This is a follow-up on How do you change the default widget for all Django date fields in a ModelForm?.

Suppose you have a very large number of models (e.g. A-ZZZ) that is growing with the input of other developers that are beyond your control, and you want to change the way all date fields are entered (i.e. by using jQueryUI). What's the best way to ensure that all date fields are filled out using that new widget?

One suggestion from the cited question was:

def make_custom_datefield(f):
   if isinstance(f, models.DateField):
       # return form field with your custom widget here...
   else:
       return f.formfield()

class SomeForm(forms.ModelForm): 
   formfield_callback = make_custom_datefield

   class Meta:
       # normal modelform stuff here...

However, is this possible to do where you don't have explicit ModelForm's, but url patterns come from models directly? i.e. your url config is likeso:

url(r'^A/?$', 'list_detail.object_list', SomeModelA)

where SomeModelA is a model (not a form) that's turned into a ModelForm by Django in the background.

At present in my system there are no Forms for each Model. The only point of creating forms explicitly would be to add the formfield_callback suggested in the prior solution, but that goes against DRY principles, and would be error prone and labour intensive.

I've considered (as suggested in the last thread) creating my own field that has a special widget and using that instead of the builtin. It's not so labour intensive, but it could be subject to errors (nothing a good grep couldn't fix, though).

Suggestions and thoughts are appreciated.

Answer 1

It sounds like you want to do this project-wide (ie: you're not trying to do this in some cases, but in ALL cases in your running application).

One possibility is to replace the widget attribute of the DateField class itself. You would need to do this in some central location... something that is guaranteed to be loaded by every running instance of the django app. Middleware can help with this. Otherwise, just put it in the __init__ file of your app.

What you want to do is re-assign the widget property for the forms.DateField class itself. When a new DateField is created, Django checks to see if the code specifies any particular widget in the field property definition. If not, it uses the default for DateField. I'm assuming that if a user in your scenario really defined a particular widget, you'd want to honour that despite the change to your global API.

Try this as an example of forcing the default to some other widget... in this case a HiddenInput:

from django import forms
forms.DateField.widget = forms.HiddenInput

class Foo(forms.Form):
    a = forms.DateField()

f = Foo()
print f.fields['a'].widget
# results in <django.forms.widgets.HiddenInput object at 0x16bd910>