Django嵌套模型字段序列化报错：QuerySet无法JSON序列化

问题背景 #

模型定义如下：

class SurveyAnswer(models.Model):
    id = models.UUIDField(default=uuid.uuid4, unique=True,
        primary_key=True, editable=False)
    survey=models.ForeignKey("Survey",on_delete=models.CASCADE)
    answer=models.ForeignKey("Answer",on_delete=models.CASCADE)
    total_count=models.IntegerField(null=True,blank=True)
    total_percentage=models.FloatField(null=True,blank=True)

    class Meta:
        db_table="SurveyAnswer"


class Answer(models.Model):
    id = models.UUIDField(default=uuid.uuid4, unique=True,
        primary_key=True, editable=False)
    name= models.CharField(max_length=100)

    def __str__(self) -> str:
        return self.name
    class Meta:
        db_table="Answer"

需求是获取所有SurveyAnswer记录及关联Answer的name字段，但现有序列化器报错Object of type QuerySet is not JSON serializable，序列化器代码：

class SurveyAnswerSerializer(serializers.ModelSerializer):
    answers=serializers.StringRelatedField()

    class Meta:
        model=SurveyAnswer
        fields=["id","total_count","total_percentage","answers",]

尝试转成列表查询后返回空对象：

survey_answers=list(SurveyAnswer.objects.filter(survey=survey).select_related('answer'))
data=SurveyAnswerSerializer(survey_answers).data

解决方法 #

1. 修正序列化器字段名与参数

SurveyAnswer中外键字段是answer（单数），不是answers，同时StringRelatedField需要指定read_only=True。如果只想获取Answer的name字段，有两种简洁实现方式：

class SurveyAnswerSerializer(serializers.ModelSerializer):
    # 方法一：利用Answer的__str__方法返回name
    answer = serializers.StringRelatedField(read_only=True)
    # 方法二：直接指定取name字段，逻辑更明确
    # answer = serializers.SlugRelatedField(slug_field='name', read_only=True)

    class Meta:
        model = SurveyAnswer
        fields = ["id", "total_count", "total_percentage", "answer"]

2. 序列化集合数据时添加many=True

当序列化多条数据（QuerySet或列表）时，必须在序列化器实例化时传入many=True，否则无法正确处理集合类型：

survey_answers = SurveyAnswer.objects.filter(survey=survey).select_related('answer')
# 关键：添加many=True标识处理多条数据
data = SurveyAnswerSerializer(survey_answers, many=True).data

错误原因说明 #

• 最初的序列化报错：一是序列化器字段名写错（answers对应不上模型的answer外键），二是序列化多条数据未传入many=True，导致无法识别QuerySet类型。
• 转成列表后返回空对象：依然未修正字段名错误，也没加many=True，序列化器无法正确解析集合数据，最终返回空结构。

内容的提问来源于stack exchange，提问作者ftdeveloper