Daniel Roy Greenfeld

Daniel Roy Greenfeld

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Adding Django form instance attributes

Sometimes in the clean(), clean_FOO or save() methods of a Django form, you need to have additional form instance attributes available. A sample case for this is having user_id available. This is a simple example of how to do it in Class-Based Views.

Assuming this form:

from django import forms

from .models import MyModel

class MyForm(forms.ModelForm):

    class Meta:
        model = MyModel

    def __init__(self, user_id, *args, **kwargs):
        super(MyForm, self).__init__(*args, **kwargs)

        # set the user_id as an attribute of the form
        self.user_id = user_id

Now that the form is defined, the view needs to inject the form with the user id:

from django.views.generic import UpdateView

# this assumes that django-braces is installed
from braces.views import LoginRequiredMixin

from .forms import MyForm
from .models import MyModel

class MyUpdateView(LoginRequiredMixin, UpdateView):
    model = MyModel
    form_class = MyForm
    success_url = "/someplace/"

    def get_form_kwargs(self):
        """This method is what injects forms with their keyword
        # grab the current set of form #kwargs
        kwargs = super(MyUpdateView, self).get_form_kwargs()
        # Update the kwargs with the user_id
        kwargs['user_id'] = self.request.user.pk
        return kwargs

Additional Notes

You can use this technique with:

  • forms.Form
  • forms.ModelForm
  • CreateView
  • FormView
  • UpdateView

As always, https://ccbv.co.uk is a great resource for deliving into Django forms.

While this technique is used by django-braces through the UserFormKwargsMixin and UserKwargModelFormMixin mixins, it's useful to know how to do it outside that very useful tool. The reason being that attaching the user object or user_id is just one option out of many.


This should also work with django-vanilla-views, but I haven't tested it yet.


See you at BarCamp Django SF!

On October 4th and 5th I'll be at BarCamp Django SF if you want to talk about Django, Python, or have me teach you how to do cartwheels.

Tags: python django howto class-based-views forms
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