如何在Django Rest Framework中序列化多个到多个字段

Question

I have a model called UserProfile which is a OneToOneField to the default User model. I have a Post model which has User as ManyToManyField . I am unable to write a serializer for Post which includes User in responses.

My UserProfile model:

class UserProfile(models.Model):
    user = models.OneToOneField(User)
    name = models.CharField(max_length=255, null=True)
    profile_picture = models.CharField(max_length=1000, null=True)

My Post model:

class Post(models.Model):
    text = models.TextField(null=True)
    title = models.CharField(max_length=255, null=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    user = models.ManyToManyField(User)

My Post serializer:

class PostSerializer(serializers.ModelSerializer):
    users = UserProfileSerializer(source='user.userprofile', many=True)

    class Meta:
        model = Post
        fields = ('id', 'text', 'title', 'users')

With above serializer I am getting the following error:

Got AttributeError when attempting to get a value for field `users` on serializer `WorkSerializer`.
The serializer field might be named incorrectly and not match any attribute or key on the `Work` instance.
Original exception text was: 'ManyRelatedManager' object has no attribute 'userprofile'.

EDIT : I created another serializer UserSerializerForPost which is used in PostSerializer :

class UserSerializerForPost(serializers.ModelSerializer):
    user = UserProfileSerializer(source='userprofile')

    class Meta:
        model = User
        fields = ('user',)


class PostSerializer(serializers.ModelSerializer):
    users = UserSerializerForPost(source='user', many=True)

    class Meta:
        model = Post
        fields = ('id', 'text', 'title', 'users')

Though this works, but I am getting UserProfile response in a dictionary of user as users list:

"users": [
  {
    "user": {
      "id": 2,
      ...
  },
  {
    "user": {
      "id": 4,
      ...
    }
  }
]

But I want:

"users": [
  {
    "id": 2,
    ...
  },
  {
    "id": 4,
    ...
    }
  }
],

Answer 1

Following solution worked for me and it did not even require creating UserSerializerForPost :

class PostSerializer(serializers.ModelSerializer):
    users = serializers.SerializerMethodField()

    class Meta:
        model = Post
        fields = ('id', 'text', 'title', 'users')

    def get_users(self, obj):
        response = []
        for _user in obj.user.all():
            user_profile = UserProfileSerializer(
                _user.userprofile,
                context={'request': self.context['request']})
            response.append(user_profile.data)
        return response

EDIT : Okay I found a even better approach than the above. First add a get_user_profiles to Post :

class Post(models.Model):
    text = models.TextField(null=True)
    title = models.CharField(max_length=255, null=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    user = models.ManyToManyField(User)

    def get_user_profiles(self):
        return UserProfile.objects.filter(user__post=self)

Then I updated my PostSerializer with:

class PostSerializer(serializers.ModelSerializer):
    users = UserProfileSerializer(source='get_user_profiles', many=True)

    class Meta:
        model = Post
        fields = ('id', 'text', 'title', 'users')

This is way too cleaner version that earlier one.