Override Django formset delete behavior: Delete form instance if empty field in Django model formset

Question

I run into this often:

I want to hide the default delete box in formsets and delete the instance of an object if a certain field is cleared in the each form of the formset.

The typical problem is that, either validation gets in the way or this breaks the blank form detection and starts adding all forms ( even blank extra ) when the formset is saved.

Bobort · Accepted Answer · 2015-12-02 15:44:31Z

5

Here is the solution I found:

This code creates a model formset, ensures it validates by permitting a blank field, and then on save determines which objects to delete and which forms to save.

TaskFormset = inlineformset_factory(User, FAQ, extra=3, can_delete=False, exclude=('user', 'answer',))
formset = TaskFormset(request.POST, request.FILES, instance=user)
for form in formset:
    form.fields['question'].required = False

// later when performing the formset save

for form in formset:
    if form.instance.pk and form.cleaned_data['question'].strip() == '':
        form.instance.delete()
    elif form.cleaned_data:
        form.save()

edited Dec 2, 2015 at 15:44

Bobort

3,23835 silver badges45 bronze badges

answered Jun 25, 2013 at 17:50

Paul Kenjora

2,01419 silver badges20 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Kiran Ruth R Over a year ago

u can probably add some javascript which sets the delete flag to true when the field is empty .

Foo Party Over a year ago

No Kiran, he will want to do that processing server side. Relying on javascript to do that is the same as accepting the user's judgement.

Paul Kenjora Over a year ago

Controlling the form in the formset seems more pythonic than adding external JS code. This is easier to test and seems simpler than adding JS and CSS overhead. Thank you for the suggestions.

Tim Tisdall · Accepted Answer · 2017-12-19 21:48:14Z

There's a method on BaseFormSet called _should_delete_form which makes it easy to automatically delete an instance based on your own criteria, however it's a "private" method so not sure about future support. You also need to save the formsets by calling formset.save().

In the example below it will delete a row if all the fields values evaluate to false values.

class MyFormSet(forms.BaseInlineFormSet):
    def _should_delete_form(self, form):
        """Return whether or not the form should be deleted."""
        if form.cleaned_data.get(forms.formsets.DELETION_FIELD_NAME):
            return True  # marked for delete
        fields = ('name', 'question', 'amount', 'measure', 'comment')
        if not any(form.cleaned_data[i] for i in fields):
            return True
        return False

Collectives™ on Stack Overflow

Override Django formset delete behavior: Delete form instance if empty field in Django model formset

2 Answers 2

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related