How to show related items using DeleteView in Django?

Question

I am doing a view to delete (using the generic view DeleteView from Django) an instance from a model, but it cascades and deletes instances from other models:

url(r'^person/(?P<pk>\d+)/delete/$', login_required(DeleteView.as_view(model=Person, success_url='/person/', template_name='delete.html')), name='person_delete'),

What I want to do is to show the list of related items that are going to be deleted, as the admin interface does, like:

Are you sure you are going to delete Person NAMEOFTHEPERSON?
By deleting it, you are also going to delete:
CLASSNAME1: CLASSOBJECT1 ; CLASSNAME2: CLASSOBJECT2 ; CLASSNAME3: CLASSOBJECT3 ; etc

score 54 · Accepted Answer · edited Dec 19 '17 at 08:29

You can use the Collector class Django uses to determine what objects to delete in the cascade. Instantiate it and then call collect on it passing the objects you intend to delete. It expects a list or queryset, so if you only have one object, just put in inside a list:

from django.db.models.deletion import Collector

collector = Collector(using='default') # or specific database
collector.collect([some_instance])
for model, instance in collector.instances_with_model():
    # do something

instances_with_model returns a generator, so you can only use it within the context of a loop. If you'd prefer an actual data structure that you can manipulate, the admin contrib package has a Collector subclass called NestedObjects, that works the same way, but has a nested method that returns a hierarchical list:

from django.contrib.admin.utils import NestedObjects

collector = NestedObjects(using='default') # or specific database
collector.collect([some_instance])
to_delete = collector.nested()

Updated: Since Django 1.9, django.contrib.admin.util was renamed to django.contrib.admin.utils

Note that Collector does not resolve many-to-many fields, you need to use NestedObjects to do that. — Emil Stenström, Jun 25 '13 at 13:18

score 7 · Answer 2 · answered Sep 16 '16 at 14:10

I use a cutdown modifcation of get_deleted_objects() from the admin and use it to extend my context in get_context in the delete view:

define somewhere

from django.contrib.admin.utils import NestedObjects
from django.utils.text import capfirst
from django.utils.encoding import force_text

def get_deleted_objects(objs): 
    collector = NestedObjects(using='default')
    collector.collect(objs)
    #
    def format_callback(obj):
        opts = obj._meta
        no_edit_link = '%s: %s' % (capfirst(opts.verbose_name),
                                   force_text(obj))
        return no_edit_link            
    #
    to_delete = collector.nested(format_callback)
    protected = [format_callback(obj) for obj in collector.protected]
    model_count = {model._meta.verbose_name_plural: len(objs) for model, objs in collector.model_objs.items()}
    #
    return to_delete, model_count, protected

then in your views

from somewhere import get_deleted_objects
#
class ExampleDelete(DeleteView):
    # ...
    def get_context_data(self, **kwargs):
        #
        context = super().get_context_data(**kwargs)
        #
        deletable_objects, model_count, protected = get_deleted_objects([self.object])
        #
        context['deletable_objects']=deletable_objects
        context['model_count']=dict(model_count).items()
        context['protected']=protected
        #
        return context

now you can use them in your template

<table>
  <tr>
    <th>Name</th>
    <th>Amount</th>
  </tr>
  {% for model_name, object_count in model_count %}
    <tr>
      <td>{{ model_name|capfirst }}</td>
      <td>{{ object_count }}</td>
    </tr>
  {% endfor %}
</table>
<p>
  <ul>
    {{ deletable_objects|unordered_list }}
  </ul>
</p>

Most is just copy/paste/edit/delete unwanted from django admin

This works fine. On a many to many with self referencing, to_delete contains also something like 'From_company-to_company relationship: Company_contractor object (13)'. How to show properly also this kind of relationship? — cwhisperer, Feb 27 '19 at 08:58

How to show related items using DeleteView in Django?

2 Answers2

define somewhere

then in your views

now you can use them in your template

Most is just copy/paste/edit/delete unwanted from django admin

Linked

Related