如何用Django Serializers实现用户及关联评论列表序列化

Got it, let's tweak your serializers to produce the exact JSON structure you're looking for. Here's a step-by-step breakdown:

1. Update the Comment Serializer #

First, we need to trim down the CommentSerializer to only include the fields we want in the comments array (id and comment), since we don't need to return the created_by field there:

class CommentSerializer(serializers.ModelSerializer):
    class Meta:
        model = UserComments
        fields = ('id', 'comment')  # Removed 'created_by' as it's not needed in the comments list

2. Modify the User Serializer to Include Comments #

Next, we'll add a nested serializer field to UserSerializer to pull in the user's associated comments. This relies on the reverse relationship between Users and UserComments:

Option A: If your model uses related_name='comments' #

If your UserComments model's created_by ForeignKey is defined with related_name='comments' (like below), this is straightforward:

# Inside your UserComments model
created_by = models.ForeignKey(Users, on_delete=models.CASCADE, related_name='comments')

Then update the UserSerializer:

class UserSerializer(serializers.ModelSerializer):
    # Nested serializer for comments, many=True since one user has multiple comments
    comments = CommentSerializer(many=True, read_only=True)

    class Meta:
        model = Users
        fields = ('id', 'name', 'comments')  # Add 'comments' to the output fields

Option B: If you don't have related_name set #

If you didn't specify a related_name, Django uses the default reverse relationship name: usercomments_set. To map this to the comments key in your JSON, use the source parameter:

class UserSerializer(serializers.ModelSerializer):
    comments = CommentSerializer(many=True, read_only=True, source='usercomments_set')

    class Meta:
        model = Users
        fields = ('id', 'name', 'comments')

3. Optimize Query Performance (Important!) #

To avoid the N+1 query problem (where we fetch each user's comments with a separate query), use prefetch_related in your view when fetching users:

from rest_framework.response import Response
from rest_framework.views import APIView

class UserListView(APIView):
    def get(self, request):
        # Prefetch related comments to optimize queries
        users = Users.objects.all().prefetch_related('comments')
        serializer = UserSerializer(users, many=True)
        return Response(serializer.data)

Result #

With these changes, your API will return exactly the JSON structure you requested:

[ 
 { 
 "id":1, 
 "name":"Tony", 
 "comments":[ 
 { "id":1, "comment":"This is a test comment" }, 
 { "id":2, "comment":"This is a test comment2" } 
 ] 
 }, 
 { 
 "id":2, 
 "name":"Alaric", 
 "comments":[ 
 { "id":3, "comment":"This is a test comment3" }, 
 { "id":4, "comment":"This is a test comment4" } 
 ] 
 } 
 ]

内容的提问来源于stack exchange，提问作者MadhuP