ValueError at /news/ Value: None must be instance of Model: <class 'django.db.models.base.Model'>

[Sagar]

Hi,
I'm trying to create embedded documents in mongodb using django. I'm facing this error when I tried to insert a post in database.
"ValueError at /post/Value: None must be instance of Model: <class 'django.db.models.base.Model'>"
Here is my code.
models.py

from djongo import models

# Schema for comments collection which include in belonging post

class Comments(models.Model):

username = models.CharField(max_length=25, blank=False)

comment = models.TextField()

time_stamp = models.DateTimeField(auto_now_add=True)

# Schema for post collection

class Post(models.Model):

username = models.CharField(max_length=25, blank=False)

title = models.CharField(max_length=100, blank=False)

post = models.TextField()

time_stamp = models.DateTimeField(auto_now_add=True)

comments = models.EmbeddedModelField('Comments')

# allows to use all functionality of django orm

objects = models.DjongoManager()

def __str__(self):

return self.post

serializers.py

from rest_framework import serializers

from models import Post, Comments

class PostSerializer(serializers.ModelSerializer):

class Meta:

model = Post

fields = ('id', 'username', 'title', 'post', 'time_stamp')

class CommentsSerializer(serializers.ModelSerializer):

class Meta:

model = Comments

fields = '__all__'

views.py

from rest_framework_mongoengine import generics

from serializers import PostSerializer, CommentsSerializer

from models import Post, Comments

class PostAPIView(generics.CreateAPIView):

lookup_field = 'id'

serializer_class = PostSerializer

def get_queryset(self):

return Post.__objects.all()

class CommentsAPIView(generics.CreateAPIView):

lookup_field = 'id'

serializer_class = CommentsSerializer

def get_queryset(self):

return Comments.__objects.all()

what is the problem with the code? Is this right method to create embedded documents in mongodb?
I used python3.6.4, django2.1, djongo1.2.29 and other libraries like pymongo and mongoengine

[Mikhailo Keda]

Not sure what you are using but all packages for Django + MongoDB are outdated.

Why do not use PostgreSQL instead of MongoDB?

[Sagar]

Hi Mikhailo
Yes you are right, but I didn't used django-nonrel or djangotoolbox. Those were totally outdated. I have used djongo which is updated as far as I know. About MongoDB, I'm working on project in which we used MongoDB. We want to use NoSQL database insted of SQL database. Did you work with django and mongodb before?

[Jason]

We want to use NoSQL database insted of SQL database

Is your data relational, and are you going to be doing alot of joins?  If so, using mongo will be a pain in your application for performance. 

I really hope you have a solid technical reason why to use mongo rather than "ITS WEBSCALE!!!!!"

[Mikhailo Keda]

rest_framework_mongoengine was updated 1 year ago, according to djongo docs they have integration with Django Rest Framework, try to use Django Rest Framework instead of rest_framework_mongoengine.
And you need debug the error.

понеділок, 20 серпня 2018 р. 14:36:15 UTC+3 користувач Sagar написав:

[Sagar]

Hi Mikhailo
I think the problem is with views. Because when I run the API, it is giving me the default root view that django provide for API. When I entered the values in form and then
when i post the data, at that time I'm getting this error.
In serializers When I make a small change It is showing me different error like this.
"AssertionError at /post/
No exception message supplied"
here is the code for serializers that I modify
serializers.py

from rest_framework import serializers

from models import Post, Comments

class PostSerializer(serializers.ModelSerializer):

class Meta:

model = Post

fields = '__all__'

class CommentsSerializer(serializers.ModelSerializer):

class Meta:

model = Comments

fields = '__all__'

I'm new to django. Can you tell me how can I debug the code? Should I use try-catch?

[ganesh c]

Hi Sagar,

 I am facing the similar issue while adding User model as embeddedmodel in a custom profile model.

Please let me know do you get any solutions for your issue,

Thanks,

Ganesh

[team.a...@gmail.com]

This usually happens when you have added and EmbeddedModel and not passing any value to that field while creation.
Hope this helps.

[mahesh boini]

import proper package you were importing "djongo" it should be "django".

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