Django REST framework - Serializer relations User.username - django

Question

Im working on a django project, and I have a model that looks like this:
class Comment(models.Model):
user = models.ForeignKey(settings.AUTH_USER_MODEL, default=1,on_delete=models.CASCADE)
slug = models.SlugField(unique=True,null=True, blank=True)
content_type = models.ForeignKey(ContentType, on_delete=models.CASCADE)
object_id = models.PositiveIntegerField()
content_object = GenericForeignKey('content_type', 'object_id')
parent = models.ForeignKey("self", null=True, blank=True,on_delete=models.CASCADE)
content = models.TextField()
timestamp = models.DateTimeField(auto_now_add=True)
objects = CommentManager()
def __str__(self):
return str(self.user.username)
I use this serializer:
class CommentDetailSerializer(ModelSerializer):
user = SerializerMethodField()
replies = SerializerMethodField()
class Meta:
model = Comment
fields = [
'user',
'content',
'replies',
'timestamp'
]
def get_user(self,obj):
return str(obj.user.username)
def get_replies(self,obj):
if obj.is_parent:
return CommentChildSerializer(obj.children(),many=True).data
for this view:
class CommentDetailApiView(RetrieveAPIView):
queryset = Comment.objects.all()
serializer_class = CommentDetailSerializer
lookup_field = 'slug'
here is the PostSerializer I use,
class PostSerializer(ModelSerializer):
user = SerializerMethodField()
comments = SerializerMethodField()
class Meta:
model = Post
fields = [
'user',
'title',
'content',
'comments'
]
def get_user(self,obj):
return str(obj.user.username)
def get_comments(self,obj):
comments_qs = Comment.objects.filter_by_instance(obj)
comments = CommentSerializer(comments_qs, many=True).data
return comments
this is what I get in the PostDetailAPIView:
{
"user": "abc",
"title": "blabla",
"content": "bla",
"comments": [
{
"user": 1,
"content": "hey",
"timestamp": "2020-02-18T00:07:29.932850Z"
}
]
}
How do I get the comment user username instead of its id?
I get the username of the comment user only in the CommentDetailApiView.
Thank you

Answer 1

I added the get_user method to the CommentSerializer and now it works:
class CommentSerializer(serializers.ModelSerializer):
user = SerializerMethodField()
class Meta:
model = Comment
fields = [
'user',
'content',
'timestamp'
]
def get_user(self,obj):
return str(obj.user.username)

Answer 2

You can add an UserSerializer to indicate what you want to show of the user:
from django.contrib.auth.models import User
class UserSerializer(serializers.ModelSerializer):
class Meta:
model = User
fields = ('username',)
class CommentDetailSerializer(ModelSerializer):
user = UserSerializer()
..... # the rest of your code

Answer 3

You need to override to_representation() function just like below:
def to_representation(self, instance):
"""Convert `username` to lowercase."""
ret = super().to_representation(instance)
ret['username'] = ret['username'].lower()
return ret
The above code is just an example. It will return username in lowercase letters. In your case just change the line
ret['username'] = ret['username'].lower()
to
ret['username'] = self.validated_data['username']

Answer 4

StringRelatedField may be used to represent the target of the relationship using its __str__ method.
For example, the following serializer.
class CommentDetailSerializer(serializers.ModelSerializer):
user = serializers.StringRelatedField()
...
class Meta:
model = Comment
fields = [
'user',
'content',
'replies',
'timestamp'
]
...