[Answered ]-Using class-based UpdateView on a m-t-m with an intermediary model

As Berislav Lopac says:

class CategoryView(UpdateView):
    model=Category
    def form_valid(self, form):
        self.object = form.save(commit=False)
        IntermediateModel.objects.filter(category = self.object).delete()
        for other_side_model_object in form.cleaned_data['other_side_model_field']:
            intermediate_model = IntermediateModel()
            intermediate_model.category = self.object
            intermediate_model.other_side_model_related_field= other_side_model_object
            intermediate_model.save()
        return super(ModelFormMixin, self).form_valid(form)

I answer some similar here.

You should extend UpdateView and override the form_valid() method to manually save the intermediary model.

Personally, I never use generic views directly from the URL pattern, I always extend them verbatim in views.py.