如何在DRF序列化器中将employee属性设为只读并指定对应值？

现有如下Django REST Framework序列化器：

class MySerializer(serializers.ModelSerializer):
    class Meta:
        model = models.MyClass

对应的模型类：

class MyClass(models.Model):
    employee = models.ForeignKey("Employee", on_delete=models.CASCADE)
    work_done = models.TextField(blank=True, null=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

需求：

• 将employee字段设置为只读
• 该字段仅显示当前请求用户对应的Employee实例（即通过Employee.objects.get(user=self.request.user)获取的对象）

方法一：序列化器内重写to_representation方法 #

直接在序列化器中完成字段只读设置与数据过滤：

class MySerializer(serializers.ModelSerializer):
    # 标记employee为只读字段
    employee = serializers.PrimaryKeyRelatedField(read_only=True)

    class Meta:
        model = models.MyClass
        fields = ['employee', 'work_done', 'created_at', 'updated_at']

    def to_representation(self, instance):
        representation = super().to_representation(instance)
        request = self.context.get('request')
        
        if request and hasattr(request, 'user'):
            try:
                current_employee = models.Employee.objects.get(user=request.user)
                # 仅保留当前用户对应的employee数据，不匹配则置空或移除字段
                if representation['employee'] != current_employee.pk:
                    representation['employee'] = None
            except models.Employee.DoesNotExist:
                # 处理用户未关联Employee的异常情况
                representation['employee'] = None
        
        return representation

方法二：视图层配合处理（更高效） #

将数据过滤逻辑放在视图层，序列化器仅负责只读展示，减少序列化阶段的开销：

序列化器代码

class MySerializer(serializers.ModelSerializer):
    employee = serializers.PrimaryKeyRelatedField(read_only=True)

    class Meta:
        model = models.MyClass
        fields = ['employee', 'work_done', 'created_at', 'updated_at']

创建视图（以CreateAPIView为例）

class MyCreateView(generics.CreateAPIView):
    serializer_class = MySerializer

    def perform_create(self, serializer):
        # 关联当前用户对应的Employee实例
        current_employee = models.Employee.objects.get(user=self.request.user)
        serializer.save(employee=current_employee)

查询视图（以ListAPIView为例）

class MyListView(generics.ListAPIView):
    serializer_class = MySerializer

    def get_queryset(self):
        # 直接从数据库过滤出当前用户Employee关联的数据
        current_employee = models.Employee.objects.get(user=self.request.user)
        return models.MyClass.objects.filter(employee=current_employee)

方案说明 #

• 方法一适合需要对每条返回数据单独做校验的场景，但需注意捕获Employee.DoesNotExist异常，避免请求报错。
• 方法二从数据库层面直接过滤数据，性能更优，是推荐的常规做法。

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