Django rest framework serializer is valid always false

Question

I have problem with Django. I did all as was written in the tutorial but when I check is_valid on serializer there is always false.

Here is my code:

models.py
from django.db import models


class User(models.Model):
    userId = models.CharField(max_length=100)
    email = models.EmailField()

serializers.py

from .models import User
from rest_framework import serializers


class UserSerializer(serializers.ModelSerializer):
    class Meta:
        model = User
        fields = ('id', 'userId', 'email')

And then I run python manage.py shell. Then I use commands like:

from belmondoapp.models import User
from belmondoapp.serializers import UserSerializer

u = User(userId="user", email="[email protected]")
s = UserSerializer(data=u)
s.is_valid() 

And it always returns False... Why? What did I wrong?

Answer 1

After having the same problem I'd like to highlight the solution offered by @Andrea Corbellini in the comments section:

print(s.errors)

Will return a dictionary containing the fields: reason for fail. In my case this looked like:

{
'start_date': [ErrorDetail(string='Expected a date but got a datetime.', code='datetime')],
'end_date': [ErrorDetail(string='Expected a date but got a datetime.', code='datetime')],
'client': [ErrorDetail(string='Incorrect type. Expected pk value, received Client.', code='incorrect_type')]
}

I found this absolutely invaluable.

Answer 2

s = UserSerializer(data=u)

should be:

s = UserSerializer(data={"userId"="user", "email"="[email protected]"})

The serialization process (from the Model to the dictionary) doesn't require a call to is_valid:

s = UserSerializer(instance=u)
s.data

The deserialization process (from dict to Model) doesn't accept Model:

s = UserSerializer(data={"userId"="user", "email"="[email protected]"})
s.is_valid()
s.validated_data