Print the output in my desired format using nested serializers? - python-3.x

Question

I am trying to send messages using django-rest framework.I have created serializers for both user and message.I am using django default user model for storing user's details.
I am pasting my model and serializers here:
class MessageModel(models.Model):
message = models.CharField(max_length=100)
created_at = models.DateTimeField(default=now)
updated_at = models.DateTimeField(default=now)
user = models.ForeignKey(User,on_delete=models.CASCADE,related_name='user')
class UserSerializer(ModelSerializer):
class Meta:
model = get_user_model()
fields = ['id','username','email']
class MessageSerializer(ModelSerializer):
created_by = UserSerializer(read_only=True)
class Meta:
model = MessageModel
fields = ['id','message', 'created_at', 'updated_at','user','created_by']
View :
class MessageViewSet(viewsets.ModelViewSet):
authentication_classes = [TokenAuthentication]
permission_classes = [IsAuthenticated]
queryset = MessageModel.objects.all()
serializer_class = MessageSerializer
After creating message,I am getting response like below:
{
"id": 6,
"message": "Lorem ipsum",
"created_at": "2022-11-07T09:21:19.492219Z",
"updated_at": "2022-11-07T09:21:19.492237Z",
"user": 2
}
but my output should looks like in below format,everytime when a new message is created :
{
"id": 102,
"message": "Lorem ipsum",
"created_at": "created time in UTC",
"updated_at": "last updated time in UTC",
"created_by": {
"id": 3,
"username": "testuser",
"email": "test#mail.com",
}
}
In case of any error, return the error message.

Answer 1

The name of the field is user, not created_by, so:
class MessageSerializer(ModelSerializer):
user = UserSerializer(read_only=True)
class Meta:
model = MessageModel
fields = ['id', 'message', 'created_at', 'updated_at', 'user']
or you can specify user as source:
class MessageSerializer(ModelSerializer):
created_by = UserSerializer(read_only=True, source='user')
class Meta:
model = MessageModel
fields = ['id', 'message', 'created_at', 'updated_at', 'created_by']
Note: Models normally have no …Model suffix. Therefore it might be better to rename MessageModel to Message.
Note: It is normally better to make use of the settings.AUTH_USER_MODEL [Django-doc] to refer to the user model, than to use the User model [Django-doc] directly. For more information you can see the referencing the User model section of the documentation.
Note: The related_name=… parameter [Django-doc]
is the name of the relation in reverse, so from the User model to the MessageModel
model in this case. Therefore it (often) makes not much sense to name it the
same as the forward relation. You thus might want to consider renaming the user relation to messages.