django-AttributeError：“ NoneType”对象没有属性“ first_name”

Question

Would appreciate some help understanding whenever I try to setup my client I am getting the following error: AttributeError: 'NoneType' object has no attribute 'first_name' .

Here is the log:

Environment:


Request Method: GET
Request URL: http://192.168.33.10:8000/podfunnel/clientsetup/

Django Version: 1.9
Python Version: 2.7.6
Installed Applications:
('producer',
 'django.contrib.admin',
 'django.contrib.sites',
 'registration',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'storages',
 'django_extensions',
 'randomslugfield',
 'adminsortable2',
 'crispy_forms')
Installed Middleware:
('django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware',
 'django.middleware.security.SecurityMiddleware')



Traceback:

File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py" in get_response
  149.                     response = self.process_exception_by_middleware(e, request)

File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py" in get_response
  147.                     response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "/usr/local/lib/python2.7/dist-packages/django/views/generic/base.py" in view
  68.             return self.dispatch(request, *args, **kwargs)

File "/usr/local/lib/python2.7/dist-packages/django/views/generic/base.py" in dispatch
  88.         return handler(request, *args, **kwargs)

File "/home/vagrant/fullcast_project/producer/views/pod_funnel.py" in get
  110.         initial_values['first_name'] = client.first_name

Exception Type: AttributeError at /podfunnel/clientsetup/
Exception Value: 'NoneType' object has no attribute 'first_name'

It has to do in my ClientSetupView under y views.py :

class ClientSetupView(View):
form_class = ClientSetupForm
template_name = 'pod_funnel/forms.html'

# In the get we manage the request to get the form and prefill it if necessary
def get(self, request, *args, **kwargs):
    # We need to check first if the current user has a client and podcast setup,
    # if so, prepopulate. Otherwise get empty form.
    initial_values = {}
    user = request.user

    if Client.objects.filter(user=user).exists():

        client = CLient.objects.filter(user=user).first()

        initial_values['first_name'] = client.first_name
        initial_values['last_name'] = client.last_name

        podcast = Podcast.objects.filter(client=client).first()
        request.session['client_id'] = client.id

        if podcast:
            initial_values['podcast_name'] = podcast.name
            # lets store podcast_id in session so we can retrieve it directly in post
            request.session['podcast_id'] = podcast.id

    form = self.form_class(initial=initial_values)
    return render(request, self.template_name, {'form': form})

# In the the post we manage updates to the data
def post(self, request, *args, **kwargs):
    form = self.form_class(request.POST)

    if form.is_valid():
        # lets get the data
        first_name = form.cleaned_data.get('first_name')
        last_name = form.cleaned_data.get('last_name')
        podcast_name = form.cleaned_data.get('podcast_name')

        # First we see if we have a client_id in session, if so we retrieve and update
        # otherwise we create a new one.
        client_id = request.session.get('client_id', None)
        if client_id is not None:
            request.session.delete('client_id')
            client = Client.objects.get(id=client_id)
        else:
            client = Client()
        client.first_name = first_name
        client.last_name = last_name
        client.company_name = podcast_name
        client.save()

        # Now we update or create the associated podcast.
        podcast_id = request.session.get('podcast_id', None)
        if podcast_id is not None:
            request.session.delete('podcast_id')
            podcast = Podcast.objects.get(id=podcast_id)
        else:
            podcast = Podcast()
        podcast.client = client
        podcast.name = podcast_name
        podcast.save()

        success, message_list = update_or_create_preset_for_podcast(podcast)

        # in any case we can continue with additional podcast setup, but we need
        # to attempt to create the preset one more time at some point before the
        # user can create the first productions.
        return HttpResponseRedirect(reverse('podfunnel:podcastsetup'))

    return render(request, self.template_name, {'form': form})

Answer 1

The line were you check if client is not None should come immediately after reading from the database as first may return None if there are no items:

client = Client.objects.filter(user=user).first()
if client is not None:
    initial_values['first_name'] = client.first_name
    initial_values['last_name'] = client.last_name

Or you can use exists to test if there is at least one client for that user before fetching first :

if Client.objects.filter(user=user).exists():
    client = Client.objects.filter(user=user).first()
    initial_values['first_name'] = client.first_name
    initial_values['last_name'] = client.last_name

The exists approach is more efficient:

Returns True if the QuerySet contains any results, and False if not. This tries to perform the query in the simplest and fastest way possible, but it does execute nearly the same query as a normal QuerySet query.

Answer 2

According to the documentation first() would return None if there was nothing matched:

Returns the first object matched by the queryset, or None if there is no matching object.

In other words, client has a None value after executing this line:

client = Client.objects.filter(user=user).first()

which means that there was no clients for the current user.