Limit Django's inlineformset_factory to only create new objects

Question

I am using django\'s inline formset factory. To use the example in the docs,

author = Author.objects.get(pk=1)
BookFormSet = inlineformset_factory(Author, Book)         


        

Answer 1

Based on Jeremy Lewis and if you don't want to subclass BaseInlineFormSet, you can just give an empty queryset parameter to your BookFormSet.

See pseudo (untested) Django 1.6 code sample:

BookFormSet = inlineformset_factory(parent=Author, model=Book)
if request.method == "POST":
    formset = BookFormSet(request.POST, request.FILES, instance=author)
    if formset.is_valid():
        formset.save()
else:
    queryset = Book.objects.none() # does not allow to edit books
    formset = BookFormSet(instance=project, initial=initial, queryset=queryset)
return render(request, "add_book.html", { "formset": formset, })

Answer 2

inlineformset_factory takes a formset kwarg, which defaults to BaseInlineFormSet. BaseInlineFormSet subclasses BaseModelFormSet, which defines a get_queryset method. If you create a BaseInlineFormSet subclass and override get_queryset to return EmptyQuerySet(), you should get what you're after. In the above example then, it would look like this:

from django.db.models.query import EmptyQuerySet
from django.forms.models import BaseInlineFormSet

class BaseInlineAddOnlyFormSet(BaseInlineFormSet):
    def get_queryset(self):
        return EmptyQuerySet()

author = Author.objects.get(pk=1)
BookFormSet = inlineformset_factory(Author, Book, formset=BaseInlineAddOnlyFormSet)
formset = BookFormSet(request.POST, instance=author)

Answer 3

Actually the answer is given in the documentation. Just don't give any instance to the FormSet. From the doc:

>>> from django.forms.models import inlineformset_factory
>>> BookFormSet = inlineformset_factory(Author, Book)
>>> author = Author.objects.get(name=u'Mike Royko')
>>> formset = BookFormSet() # This will create an empty form with your model fields

You can then create view as follows:

if request.method == "POST":
    formset = BookFormSet(request.POST, request.FILES)
    if formset.is_valid():
        formset.save()
else:
    formset = BookFormSet()
return render_to_response("add_book.html", {
    "formset": formset,

Hope it helps.