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[英]How to serialize using django rest_framework a ManyToManyFields with a Through Model
[英]Serialize ManyToManyFields with a Through Model in Django REST Framework
我through
model 与此 M2M 关系为
class Person(models.Model):
name = models.CharField(max_length=128)
def __str__(self):
return self.name
class Group(models.Model):
name = models.CharField(max_length=128)
members = models.ManyToManyField(Person, through='Membership')
def __str__(self):
return self.name
class Membership(models.Model):
person = models.ForeignKey(Person, on_delete=models.CASCADE)
group = models.ForeignKey(Group, on_delete=models.CASCADE)
date_joined = models.DateField()
invite_reason = models.CharField(max_length=64)
请注意,我在invite_reason
中有额外的字段date_joined
和邀请原因。
现在,我想使用 DRF 序列化Group
查询集,因此我选择了下面的序列化程序设置。
class PersonSerializer(serializers.ModelSerializer):
class Meta:
model = Person
fields = "__all__"
class GroupSerializer(serializers.ModelSerializer):
members = PersonSerializer(read_only=True, many=True)
class Meta:
model = Group
fields = "__all__"
它正在返回以下响应,
[
{
"id": 1,
"members": [
{
"id": 1,
"name": "Jerin"
}
],
"name": "Developer"
},
{
"id": 2,
"members": [
{
"id": 1,
"name": "Jerin"
}
],
"name": "Team Lead"
}
]
这里的members
字段返回Person
信息,非常完美。
但,
如何将date_joined
和invite_reason
字段/信息添加到 JSON 响应的members
字段中?
class PersonSerializer(serializers.ModelSerializer):
class Meta:
model = Person
fields = "__all__"
def serialize_membership(self, person_instance): # simple method to serialize the through model fields membership_instance = person_instance \ .membership_set \ .filter(group=self.context["group_instance"]) \ .first() if membership_instance: return MembershipSerializer(membership_instance).data return {} def to_representation(self, instance): rep = super().to_representation(instance) return {**rep, **self.serialize_membership(instance)}
class MembershipSerializer(serializers.ModelSerializer): # create new serializer to serialize the through model fields class Meta: model = Membership fields = ("date_joined", "invite_reason")
class GroupSerializer(serializers.ModelSerializer):
members = serializers.SerializerMethodField() # use `SerializerMethodField`, can be used to pass context data def get_members(self, group): return PersonSerializer( group.members.all(), many=True, context={"group_instance": group} # should pass this `group` instance as context variable for filtering ).data
class Meta:
model = Group
fields = "__all__"
笔记:
PersonSerializer
的to_representation(...)
方法以将额外数据注入JSON 的members
字段person
instance/pk 和group
instance/pk 来识别要序列化的Membership
实例。 为此,我们使用了序列化器上下文来传递基本数据
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