django drf to_representation-例子

from django.db import models


class TestModel(models.Model):
   name = models.CharField(_("名称"), max_length=50, null=True, blank=True, default="")
   status = models.CharField(_("状态"), max_length=10, null=True)
   create_by = models.ForeignKey(to='users.User', on_delete=models.SET_NULL, null=True)
   liked_by = models.ManyToManyField(to='users.User')


from rest_framework import serializers


class TestSerializer(serializers.ModelSerializer):
   class Meta:
       model = TestModel
       fields = '__all__'

   def to_representation(self, instance):
       # 调用父类获取当前序列化数据，instance代表每个对象实例obj
       data = super().to_representation(instance)
       # 对原字段的值作修改
       data['create_by'] = instance.create_by.name  # 显示用户表的名称，而不是用户ID
       # 添加新的字段--model没有的字段
       data['total_likes'] = instance.liked_by.count()  # 统计数量
       return data