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Python Django REST Framework Security and Customization Add Custom Field

Eric Shelby
Eric Shelby
28,300 Points

Add Custom Field Challenge

According to the instructions: "It'd be great to show users what the average score is for a Game. Use serializers.SerializerMethodField and a custom method on the GameSerializer class to add a field named average_score. You can calculate the average score with the Avg class from Django, which I've already imported, to average the scores for the game. You can get the scores through Game.scores.all()."

However, I have been unable to solve the problem, and the documentation and example in Workspaces have been no matter. Some guidance would be appreciated.

scorekeeper/serializers.py
from django.db.models import Avg

from rest_framework import serializers

from . import models


class GameSerializer(serializers.ModelSerializer):
    average_score = serializers.SerializerMethodField()
    class Meta:
        fields = ('id', 'name')
        model = models.Game

    def get_average_score(self, obj):
        average = Game.scores.all().obj.aggregate(average_score=Avg('score'))
        if average is None:
            return 0
        return round(average*2)/2


class PlayerSerializer(serializers.ModelSerializer):
    class Meta:
        fields = ('id', 'name', 'age', 'parent_approval')
        model = models.Player

    def validate(self, data):
        if data['age'] < 13 and not data['parent_approval']:
            raise serializers.ValidationError(
                "Children under 13 require parental approval"
            )
        return data


class ScoreSerializer(serializers.ModelSerializer):
    game = serializers.HyperlinkedRelatedField(
        read_only=True, view_name='apiv2:game-detail')
    player = serializers.HyperlinkedRelatedField(
        read_only=True, view_name='apiv2:player-detail')

    class Meta:
        fields = ('id', 'game', 'player', 'score')
        model = models.Score

3 Answers

Eric Shelby
Eric Shelby
28,300 Points

Update: I now know I supposed to add 'average_score' to the 'fields', but that is the only breakthrough I've made so far.

Eric Shelby
Eric Shelby
28,300 Points

Update: I progressed to def get_average_score(self, obj): average = Game.scores.all().aggregate(Avg('score')).get('score__avg')

    if average is None:
        return 0
    return average

However, the challenge doesn't accept this. If I'm close to the answer, any improvement to this would be appreciated.

Eric Shelby
Eric Shelby
28,300 Points

Update: finally figured this out. I removed the "if" condition and replaced "Game" with "obj". I had a feeling "obj" had to be used in there somewhere. I just didn't know where. I managed to stumble another forum about the question that gave me the answer I needed.