Override save_model on Django InlineModelAdmin

Question

I have a model that has a user field that needs to be auto-populated from the currently logged in user. I can get it working as specified here if the user

Answer 1

I know I'm late to the party, but here's my situation and what I came up with, which might be useful to someone else in the future.

I have 4 inline models that need the currently logged in user.

• 2 as a created_by type field. (set once on creation)
• and the 2 others as a closed_by type field. (only set on condition)

I used the answer provided by rafadev and made it into a simple mixin which enables me to specify the user field name elsewhere.

The generic formset in forms.py

from django.forms.models import BaseInlineFormSet

class SetCurrentUserFormset(forms.models.BaseInlineFormSet):
    """
    This assume you're setting the 'request' and 'user_field' properties
    before using this formset.
    """
    def save_new(self, form, commit=True):
        """
        This is called when a new instance is being created.
        """
        obj = super(SetCurrentUserFormset, self).save_new(form, commit=False)
        setattr(obj, self.user_field, self.request.user)
        if commit:
            obj.save()
        return obj

    def save_existing(self, form, instance, commit=True):
        """
        This is called when updating an instance.
        """
        obj = super(SetCurrentUserFormset, self).save_existing(form, instance, commit=False)
        setattr(obj, self.user_field, self.request.user)
        if commit:
            obj.save()
        return obj

Mixin class in your admin.py

class SetCurrentUserFormsetMixin(object):
    """
    Use a generic formset which populates the 'user_field' model field
    with the currently logged in user.
    """
    formset = SetCurrentUserFormset
    user_field = "user" # default user field name, override this to fit your model

    def get_formset(self, request, obj=None, **kwargs):
        formset = super(SetCurrentUserFormsetMixin, self).get_formset(request, obj, **kwargs)
        formset.request = request
        formset.user_field = self.user_field
        return formset

How to use it

class YourModelInline(SetCurrentUserFormsetMixin, admin.TabularInline):
    model = YourModel
    fields = ['description', 'closing_user', 'closing_date']
    readonly_fields = ('closing_user', 'closing_date')
    user_field = 'closing_user' # overriding only if necessary

Be careful...

...as this mixin code will set the currently logged in user everytime for every user. If you need the field to be populated only on creation or on specific update, you need to deal with this in your model save method. Here are some examples:

class UserOnlyOnCreationExampleModel(models.Model):
    # your fields
    created_by = # user field...
    comment = ...

    def save(self, *args, **kwargs):
        if not self.id:
            # on creation, let the user field populate
            self.date = datetime.today().date()
            super(UserOnlyOnCreationExampleModel, self).save(*args, **kwargs)
        else:
            # on update, remove the user field from the list
            super(UserOnlyOnCreationExampleModel, self).save(update_fields=['comment',], *args, **kwargs)

Or if you only need the user if a particular field is set (like boolean field closed) :

def save(self, *args, **kwargs):

    if self.closed and self.closing_date is None:
        self.closing_date = datetime.today().date()
        # let the closing_user field set
    elif not self.closed :
        self.closing_date = None
        self.closing_user = None # unset it otherwise

    super(YourOtherModel, self).save(*args, **kwargs)  # Call the "real" save() method.

This code could probably be made way more generic as I'm fairly new to python but that's what will be in my project for now.