Make it easier to alter a model saved by the admin (e.g. add the user that created or updated it)

[simon]

A very common requirement for customising the admin is to automatically update a created_by or updated_by field with the user object that made changes to an object. This is currently way harder than it should be: ​http://www.djangosnippets.org/snippets/903/

I propose adding an extra subclassable method that makes it trivial to intercept the model as it is being created and perform additional work on it. Here's an example (incomplete) patch illustrating the idea: ​http://code.djangoproject.com/attachment/ticket/8005/8005.1.diff

This would allow ModelAdmin subclasses to make additional changes to the model by calling form.save(commit=False) instead. For the admin user described above, the subclass would look like this:

class ArticleAdmin(admin.ModelAdmin):
    
    def save_model_add(self, request, form, formsets):
        new_object = form.save(commit=False)
        new_object.created_by = request.user
        new_object.updated_by = request.user
        new_object.save()
        
        if formsets:
            for formset in formsets:
                formset.instance = new_object
                formset.save()
        
        return new_object
    
    def save_model_change(self, request, form, formsets):
        new_object = form.save(commit=False)
        new_object.updated_by = request.user
        new_object.save()
        
        if formsets:
            for formset in formsets:
                formset.save()
        
        return new_object

This is a big improvement, although I'm not too happy with the need to duplicate the formset logic. Maybe that should be split out in to a separate over-ridable method as well.

[simon]

Improved patch; refactored formset boilerplate in to a separate method

[simon]

​http://code.djangoproject.com/attachment/ticket/8005/8005.2.diff is a bit better - it lets you skip the formset boilerplate, so now the subclass looks like this:

class ArticleAdmin(admin.ModelAdmin):
    
    def save_model_add(self, request, form, formsets):
        new_object = form.save(commit=False)
        new_object.created_by = request.user
        new_object.updated_by = request.user
        new_object.save()
        return new_object
    
    def save_model_change(self, request, form, formsets):
        new_object = form.save(commit=False)
        new_object.updated_by = request.user
        new_object.save()
        return new_object

[simon]

Patch illustrating different approach, using pre_save and post_save hooks

[simon]

I've added a third option, based on feedback from Julien Phalip: ​http://code.djangoproject.com/attachment/ticket/8005/8005.2.diff

Now the subclass looks like this:

class ArticleAdmin(admin.ModelAdmin):
    
    def pre_save(self, request, instance, is_add):
        if is_add: 
            instance.created_by = request.user 
        instance.updated_by = request.user

Mailing list thread is here: ​http://groups.google.com/group/django-developers/browse_thread/thread/620b4dffa8a7f58f

[simon]

Previous comment linked to the wrong patch; should have linked to ​http://code.djangoproject.com/attachment/ticket/8005/8005.3.diff

[Julien Phalip]

I really think the pre_save and post_save hooks are the best approach here. Another example of what you could do with it:

class ArticleAdmin(admin.ModelAdmin):

     def post_save(self, request, instance, is_add):
         if is_add:
            mail_admins("New article created", "A new article created by %s in the admin. Check it out: %s" % (instance.created_by, instance.get_absolute_url()) )

[Julien Phalip]

Some other approaches have been proposed in #6406. Not sure which ticket should be considered most in this regard.

[Jacob]

This is dancing around the same problems as #6406 and #8005. For sanity's sake, let's make #6002 the master here.