AttributeError: 'AlumniResponseFormFormSet' object has no attribute 'new_objects'

Question

I'm using the Django admin and trying to make some changes to a related object that is mapped as an InlineModelAdmin object. I'm trying to do this using the save_related(self, request, form, formsets, change) method that Django provides. When I try to save something, I get an error:

AttributeError: 'AlumniResponseFormFormSet' object has no attribute 'new_objects'

Other Info:

1) I have two InlineModelAdmins
2) I'm not saving the AlumniResponseInline when this error occurs. I'm saving another InlineModelAdmin associated with the same parent model
3) Until I added the save_related() method, I wasn't having problems saving either InlineModelAdmin
4) This error is happening after all my code is executed in save_related(), so I don't have control over catching that exception

From the documentation on save_related():

The save_related method is given the HttpRequest, the parent ModelForm instance, the list of inline formsets and a boolean value based on whether the parent is being added or changed. Here you can do any pre- or post-save operations for objects related to the parent. Note that at this point the parent object and its form have already been saved.

Answer 1

I use save_formset instead of save_related and I was having the same problem until I realized that I missed two important lines inside the method:

instances = formset.save(commit=False)

at the beginning, and then, after loop instances to do something with each instance:

instance.save() #commit instance changes
formset.save_m2m() #commit the whole formset changes

at the end.

If you don't call the save_m2m() method before return, the formset object won't have the 'new_objects' attribute, needed in the construct_change_message(self, request, form, formsets) method in contrib/admin/options.py

So, this should be done for every inline you have in the main model, no matter whether you want to make something with it or not.