django restframework serializer 增加自定义字段操作

class AnimalSerializer(serializers.ModelSerializer):
 country_area = serializers.SerializerMethodField()

 class Meta:
  model = Animal
  fields = ('id', 'name', 'type','country','country_area')

 def get_country_area(self, obj):
  return obj.country.area

from .models import UserProfile
from .models import UserRole

class UserProfileSerializer(serializers.ModelSerializer):
 """
 show list serializer
 """
 role = serializers.SerializerMethodField()

 class Meta:
  model = UserProfile
  # fields = "__all__"
  fields = ["id", "username","role", "account", "really_name", "department", "tel_phone",
     "create_time", "email", "last_time", "creator"]

 def get_role(self,obj):
  user_id = obj.id
  roles = [i.role.name for i in UserRole.objects.filter(user_id=user_id)]
  roles = ",".join(roles)
  return roles

from rest_framework.utils import model_meta

 def create(self, validated_data):
  field= validated_data.pop('field_name')
  validated_data = validated_data
  instance = Model.objects.create(**validated_data)
  # ...外键表的操作
  return instance

 def update(self, instance, validated_data):
  field= validated_data.pop('field_name')
  info = model_meta.get_field_info(instance)

  for attr, value in validated_data.items():
   if attr in info.relations and info.relations[attr].to_many:
    field = getattr(instance, attr)
    field.set(value)
   else:
    setattr(instance, attr, value)
  instance.save()
  # ...
  return instance