在DRF（django-rest-framework）中，如果模型有两个foreignkeyfield，是否可以序列化？

Question

I made django project through DRF.

On my struggling with DRF, I getting wonder that it is possible to serializing these models.

models.py

class Post(models.Model):
    author = models.ForeignKey(User, related_name='related_postwriter')
    title = models.CharField(max_length=200, blank = False)
    text = models.TextField(blank = True)
    created_date = models.DateTimeField(
        default=timezone.now
        )
    point = models.PointField(null=False, blank=True)

    def __str__(self):              # __unicode__ on Python 2
        return self.title

class Comment(models.Model):
    post = models.ForeignKey('blog.Post', related_name='related_comments')
    author = models.ForeignKey(User, related_name='related_commentwriter')
    text = models.TextField(max_length=500)
    created_date = models.DateTimeField(default=timezone.now)

    def __str__(self):
        return self.text

There are two ForeignKey field in Comment model, i think it is maybe the reason serializer.py is very hard to deal with.

serializers.py

class UserSerializer(serializers.ModelSerializer):
    posts = serializers.PrimaryKeyRelatedField(many=True, read_only=True)
    comments = serializers.PrimaryKeyRelatedField(many=True, read_only=True)
    class Meta:
        model = User
        fields = ('id', 'username', 'email', 'posts')

class PostSerializer(serializers.ModelSerializer):
    class Meta:
        model = Post
        fields = ('id', 'author', 'title', 'text', 'point')
    def create(self, validated_data):
        validated_data['author'] = self.context['request'].user
        return super(PostSerializer, self).create(validated_data)


class CommentSerializer(serializers.ModelSerializer):
    class Meta:
        model = Comment
        fields = ('id', 'post', 'author', 'text')
    def create(self, validated_data):
        validated_data['author'] = self.context['request'].user
        return super(CommentSerializer, self).create(validated_data)

I thought comments = serializers.PrimaryKeyRelatedField(many=True, read_only=True) have to be placed in class PostSerializer(serializers.ModelSerializer): also, but when i placed as i thought, there comes error AssertionError at /posts/ The field 'comments' was declared on serializer PostSerializer, but has not been included in the 'fields' option. so when i put 'comments' in ther field like

class PostSerializer(serializers.ModelSerializer):
    comments = serializers.PrimaryKeyRelatedField(many=True, read_only=True)
    class Meta:
        model = Post
        fields = ('id', 'author', 'title', 'text', 'point', 'comments')

then, -> AttributeError at /posts/ 'Post' object has no attribute 'comments' is occurred.

What is my fault?

Because I want make android app that user can read a post and comments 'related with the post' at the same time(like almost community websites, reddit, facebook...), serializers.py i posted is not enough. serializers.py i posted is not seems to be sufficient for reflecting relation between post and comment.

Are there problem with comment model? Or am i wrong?

I'm new, novice at programming, Please teach me.

Thanks for reading.

Answer 1

There is nothing wrong, you are just accessing the wrong attributes. If you look at your models, you define a related name to posts:

post = models.ForeignKey('blog.Post', related_name='related_comments')

So, when you write your serializer, the "field" you should be accessing should be the related name instead of comments. Change the serializer to:

class PostSerializer(serializers.ModelSerializer):
    related_comments = serializers.PrimaryKeyRelatedField(many=True, read_only=True)
    class Meta:
        model = Post
        fields = ('id', 'author', 'title', 'text', 'point', 'related_comments')

Answer 2

您可以使用嵌套关系