Inline Form Validation in Django

Question

I would like to make an entire inline formset within an admin change form compulsory. So in my current scenario when I hit save on an Invoice form (in Admin) the inline Order form is blank. I'd like to stop people creating invoices with no orders associated.

Anyone know an easy way to do that?

Normal validation like (required=True) on the model field doesn't appear to work in this instance.

Answer 1

The best way to do this is to define a custom formset, with a clean method that validates that at least one invoice order exists.

class InvoiceOrderInlineFormset(forms.models.BaseInlineFormSet):
    def clean(self):
        # get forms that actually have valid data
        count = 0
        for form in self.forms:
            try:
                if form.cleaned_data:
                    count += 1
            except AttributeError:
                # annoyingly, if a subform is invalid Django explicity raises
                # an AttributeError for cleaned_data
                pass
        if count < 1:
            raise forms.ValidationError('You must have at least one order')

class InvoiceOrderInline(admin.StackedInline):
    formset = InvoiceOrderInlineFormset


class InvoiceAdmin(admin.ModelAdmin):
    inlines = [InvoiceOrderInline]