Issue
I am new to django and drf. I've created a viewset for getting list of elements, adding new, updating and deleting, but I have some troubles when I try to create a viewset for getting detailed info about 1 element.
Here is my urls.py
urlpatterns = [
path('tasks', views.TaskViewset.as_view(
{
'get':'list',
'post':'add',
'put':'update',
'delete':'delete'
}
)),
path('tasks/<int:pk>', views.TaskDetailViewset.as_view(
{
'get':'detail'
}
))
]
and here is my TaskDetailViewset from views.py
class TaskDetailViewset(viewsets.ViewSet):
def detail(self, request, pk, *args, **kwargs):
#data = request.query_params
task = models.Task.objects.get(id=pk)
serializer = serializers.TaskSerializer(task)
if serializer.is_valid():
return Response(data=serializer.data, status=status.HTTP_200_OK)
return Response(status=status.HTTP_404_NOT_FOUND)
When I try to send request to http://127.0.0.1:8000/api/v1/tasks/1 I get 'NoneType' object is not callable and I don't understand where is the problem here
Traceback:
Environment:
Request Method: GET
Request URL: http://127.0.0.1:8000/api/v1/tasks/1
Django Version: 4.1.2
Python Version: 3.10.0
Installed Applications:
['django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'rest_framework',
'todo']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.middleware.common.CommonMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware',
'django.middleware.clickjacking.XFrameOptionsMiddleware']
Traceback (most recent call last):
File "/Users/aleksandr/Documents/projects/todoist/venv/lib/python3.10/site-packages/django/core/handlers/exception.py", line 55, in inner
response = get_response(request)
File "/Users/aleksandr/Documents/projects/todoist/venv/lib/python3.10/site-packages/django/core/handlers/base.py", line 197, in _get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/Users/aleksandr/Documents/projects/todoist/venv/lib/python3.10/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
return view_func(*args, **kwargs)
File "/Users/aleksandr/Documents/projects/todoist/venv/lib/python3.10/site-packages/rest_framework/viewsets.py", line 125, in view
return self.dispatch(request, *args, **kwargs)
File "/Users/aleksandr/Documents/projects/todoist/venv/lib/python3.10/site-packages/rest_framework/views.py", line 509, in dispatch
response = self.handle_exception(exc)
File "/Users/aleksandr/Documents/projects/todoist/venv/lib/python3.10/site-packages/rest_framework/views.py", line 469, in handle_exception
self.raise_uncaught_exception(exc)
File "/Users/aleksandr/Documents/projects/todoist/venv/lib/python3.10/site-packages/rest_framework/views.py", line 480, in raise_uncaught_exception
raise exc
File "/Users/aleksandr/Documents/projects/todoist/venv/lib/python3.10/site-packages/rest_framework/views.py", line 506, in dispatch
response = handler(request, *args, **kwargs)
Exception Type: TypeError at /api/v1/tasks/1
Exception Value: 'NoneType' object is not callable
Update: I found in interactive debug this Here I see that handler is None but I still dont't get why
Update 2:
from rest_framework import serializers
from todo.models import Task
class TaskSerializer(serializers.Serializer):
id = serializers.IntegerField(
read_only=True
)
title = serializers.CharField(
required = True
)
content = serializers.CharField(
required=False
)
done = serializers.BooleanField(
required=True
)
def create(self, validated_data):
return Task.objects.create(**validated_data)
def update(self, instance, validated_data):
instance.title = validated_data.get('title', instance.title)
instance.content = validated_data.get('content', instance.content)
instance.done = validated_data.get('done', instance.done)
instance.save()
return instance
Solution
By rebuilding a very small experimental project, I was able to solve this problem by understanding a series of problems below and I have put the form that you can properly do what you want here for you:
- It seems that this error you are receiving (
Exception Value: 'NoneType' object is not callable
) is related to the name of thedetail
(honestly, I have not understood the reason yet and I'm searching for it) and by changing it to any other name (really any other name 😄), this error will be resolved, according to your codes like this will be:
urls.py
path('tasks/<int:pk>', views.TaskDetailViewset.as_view( {
'get':'any_other_thing'
}))
]
views.py
class TaskDetailViewset(viewsets.ViewSet):
def any_other_thing(self, request, pk): # you can send more params like *args or **kwrags and they are Ok
...
- After changing point
1
in your codes, with sending a request to mentioned url you'll encounter the following error:
AssertionError: Cannot call `.is_valid()` as no `data=` keyword argument was passed when instantiating the serializer instance.
which will be solved by adding a data=
argument name before task
on the line where you build serializer
:
def any_other_thing(self, request, pk):
...
serializer = TaskSerializer(data=task)
...
- After making the above change, you will still have problems in creating the
serializer
, and if you have made the serializer errors by placing the following line:
return Response(status=status.HTTP_404_NOT_FOUND)
In the code related to the view instead of
return Response(data=serializer.errors, status=status.HTTP_404_NOT_FOUND)
You can understand that now the error related to the non-field-error
(Instead of passing a dictionary, you passed a "task" object):
{
"non_field_errors": [
"Invalid data. Expected a dictionary, but got Task."
]
}
By adding the following function with the task
argument instead of passing the task
directly to TaskSerializer
, this problem will also be solved and you will finally be able to receive an answer successfully.
class TaskDetailViewset(viewsets.ViewSet):
def any_other_thing(self, request, pk):
...
serializer = TaskSerializer(data=model_to_dict(task))
...
Therefore, your code snippets will be as follows:
urls.py
from django.urls import path
from . import views
urlpatterns = [
path('tasks', views.TaskViewset.as_view(
{
'get':'list',
'post':'add',
'put':'update',
'delete':'delete'
}
)),
path('tasks/<int:pk>', views.TaskDetailViewset.as_view( {
'get':'any_other_thing'
}))
]
views.py
from django.forms.models import model_to_dict
from rest_framework.response import Response
from rest_framework import status, viewsets
from todo.models import Task
from todo.serilizers import TaskSerializer
class TaskDetailViewset(viewsets.ViewSet):
def any_other_thing(self, request, pk, *args, **kwargs):
#data = request.query_params
task = Task.objects.get(id=pk)
serializer = TaskSerializer(data=model_to_dict(task))
if serializer.is_valid():
return Response(data=serializer.data, status=status.HTTP_200_OK)
return Response(data=serializer.errors, status=status.HTTP_404_NOT_FOUND)
Answered By - Javad
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